diff --git a/go/vendor/github.com/globalsign/mgo/bson/bson.go b/go/vendor/github.com/globalsign/mgo/bson/bson.go
new file mode 100644
index 0000000..eb87ef6
--- /dev/null
+++ b/go/vendor/github.com/globalsign/mgo/bson/bson.go
@@ -0,0 +1,836 @@
+// BSON library for Go
+//
+// Copyright (c) 2010-2012 - Gustavo Niemeyer <gustavo@niemeyer.net>
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Package bson is an implementation of the BSON specification for Go:
+//
+//     http://bsonspec.org
+//
+// It was created as part of the mgo MongoDB driver for Go, but is standalone
+// and may be used on its own without the driver.
+package bson
+
+import (
+	"bytes"
+	"crypto/md5"
+	"crypto/rand"
+	"encoding/binary"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"os"
+	"reflect"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+//go:generate go run bson_corpus_spec_test_generator.go
+
+// --------------------------------------------------------------------------
+// The public API.
+
+// Element types constants from BSON specification.
+const (
+	ElementFloat64                byte = 0x01
+	ElementString                 byte = 0x02
+	ElementDocument               byte = 0x03
+	ElementArray                  byte = 0x04
+	ElementBinary                 byte = 0x05
+	Element06                     byte = 0x06
+	ElementObjectId               byte = 0x07
+	ElementBool                   byte = 0x08
+	ElementDatetime               byte = 0x09
+	ElementNil                    byte = 0x0A
+	ElementRegEx                  byte = 0x0B
+	ElementDBPointer              byte = 0x0C
+	ElementJavaScriptWithoutScope byte = 0x0D
+	ElementSymbol                 byte = 0x0E
+	ElementJavaScriptWithScope    byte = 0x0F
+	ElementInt32                  byte = 0x10
+	ElementTimestamp              byte = 0x11
+	ElementInt64                  byte = 0x12
+	ElementDecimal128             byte = 0x13
+	ElementMinKey                 byte = 0xFF
+	ElementMaxKey                 byte = 0x7F
+
+	BinaryGeneric     byte = 0x00
+	BinaryFunction    byte = 0x01
+	BinaryBinaryOld   byte = 0x02
+	BinaryUUIDOld     byte = 0x03
+	BinaryUUID        byte = 0x04
+	BinaryMD5         byte = 0x05
+	BinaryUserDefined byte = 0x80
+)
+
+// Getter interface: a value implementing the bson.Getter interface will have its GetBSON
+// method called when the given value has to be marshalled, and the result
+// of this method will be marshaled in place of the actual object.
+//
+// If GetBSON returns return a non-nil error, the marshalling procedure
+// will stop and error out with the provided value.
+type Getter interface {
+	GetBSON() (interface{}, error)
+}
+
+// Setter interface: a value implementing the bson.Setter interface will receive the BSON
+// value via the SetBSON method during unmarshaling, and the object
+// itself will not be changed as usual.
+//
+// If setting the value works, the method should return nil or alternatively
+// bson.ErrSetZero to set the respective field to its zero value (nil for
+// pointer types). If SetBSON returns a value of type bson.TypeError, the
+// BSON value will be omitted from a map or slice being decoded and the
+// unmarshalling will continue. If it returns any other non-nil error, the
+// unmarshalling procedure will stop and error out with the provided value.
+//
+// This interface is generally useful in pointer receivers, since the method
+// will want to change the receiver. A type field that implements the Setter
+// interface doesn't have to be a pointer, though.
+//
+// Unlike the usual behavior, unmarshalling onto a value that implements a
+// Setter interface will NOT reset the value to its zero state. This allows
+// the value to decide by itself how to be unmarshalled.
+//
+// For example:
+//
+//     type MyString string
+//
+//     func (s *MyString) SetBSON(raw bson.Raw) error {
+//         return raw.Unmarshal(s)
+//     }
+//
+type Setter interface {
+	SetBSON(raw Raw) error
+}
+
+// ErrSetZero may be returned from a SetBSON method to have the value set to
+// its respective zero value. When used in pointer values, this will set the
+// field to nil rather than to the pre-allocated value.
+var ErrSetZero = errors.New("set to zero")
+
+// M is a convenient alias for a map[string]interface{} map, useful for
+// dealing with BSON in a native way.  For instance:
+//
+//     bson.M{"a": 1, "b": true}
+//
+// There's no special handling for this type in addition to what's done anyway
+// for an equivalent map type.  Elements in the map will be dumped in an
+// undefined ordered. See also the bson.D type for an ordered alternative.
+type M map[string]interface{}
+
+// D represents a BSON document containing ordered elements. For example:
+//
+//     bson.D{{"a", 1}, {"b", true}}
+//
+// In some situations, such as when creating indexes for MongoDB, the order in
+// which the elements are defined is important.  If the order is not important,
+// using a map is generally more comfortable. See bson.M and bson.RawD.
+type D []DocElem
+
+// DocElem is an element of the bson.D document representation.
+type DocElem struct {
+	Name  string
+	Value interface{}
+}
+
+// Map returns a map out of the ordered element name/value pairs in d.
+func (d D) Map() (m M) {
+	m = make(M, len(d))
+	for _, item := range d {
+		m[item.Name] = item.Value
+	}
+	return m
+}
+
+// The Raw type represents raw unprocessed BSON documents and elements.
+// Kind is the kind of element as defined per the BSON specification, and
+// Data is the raw unprocessed data for the respective element.
+// Using this type it is possible to unmarshal or marshal values partially.
+//
+// Relevant documentation:
+//
+//     http://bsonspec.org/#/specification
+//
+type Raw struct {
+	Kind byte
+	Data []byte
+}
+
+// RawD represents a BSON document containing raw unprocessed elements.
+// This low-level representation may be useful when lazily processing
+// documents of uncertain content, or when manipulating the raw content
+// documents in general.
+type RawD []RawDocElem
+
+// RawDocElem elements of RawD type.
+type RawDocElem struct {
+	Name  string
+	Value Raw
+}
+
+// ObjectId is a unique ID identifying a BSON value. It must be exactly 12 bytes
+// long. MongoDB objects by default have such a property set in their "_id"
+// property.
+//
+// http://www.mongodb.org/display/DOCS/Object+Ids
+type ObjectId string
+
+// ObjectIdHex returns an ObjectId from the provided hex representation.
+// Calling this function with an invalid hex representation will
+// cause a runtime panic. See the IsObjectIdHex function.
+func ObjectIdHex(s string) ObjectId {
+	d, err := hex.DecodeString(s)
+	if err != nil || len(d) != 12 {
+		panic(fmt.Sprintf("invalid input to ObjectIdHex: %q", s))
+	}
+	return ObjectId(d)
+}
+
+// IsObjectIdHex returns whether s is a valid hex representation of
+// an ObjectId. See the ObjectIdHex function.
+func IsObjectIdHex(s string) bool {
+	if len(s) != 24 {
+		return false
+	}
+	_, err := hex.DecodeString(s)
+	return err == nil
+}
+
+// objectIdCounter is atomically incremented when generating a new ObjectId
+// using NewObjectId() function. It's used as a counter part of an id.
+var objectIdCounter = readRandomUint32()
+
+// readRandomUint32 returns a random objectIdCounter.
+func readRandomUint32() uint32 {
+	var b [4]byte
+	_, err := io.ReadFull(rand.Reader, b[:])
+	if err != nil {
+		panic(fmt.Errorf("cannot read random object id: %v", err))
+	}
+	return uint32((uint32(b[0]) << 0) | (uint32(b[1]) << 8) | (uint32(b[2]) << 16) | (uint32(b[3]) << 24))
+}
+
+// machineId stores machine id generated once and used in subsequent calls
+// to NewObjectId function.
+var machineId = readMachineId()
+var processId = os.Getpid()
+
+// readMachineId generates and returns a machine id.
+// If this function fails to get the hostname it will cause a runtime error.
+func readMachineId() []byte {
+	var sum [3]byte
+	id := sum[:]
+	hostname, err1 := os.Hostname()
+	if err1 != nil {
+		_, err2 := io.ReadFull(rand.Reader, id)
+		if err2 != nil {
+			panic(fmt.Errorf("cannot get hostname: %v; %v", err1, err2))
+		}
+		return id
+	}
+	hw := md5.New()
+	hw.Write([]byte(hostname))
+	copy(id, hw.Sum(nil))
+	return id
+}
+
+// NewObjectId returns a new unique ObjectId.
+func NewObjectId() ObjectId {
+	var b [12]byte
+	// Timestamp, 4 bytes, big endian
+	binary.BigEndian.PutUint32(b[:], uint32(time.Now().Unix()))
+	// Machine, first 3 bytes of md5(hostname)
+	b[4] = machineId[0]
+	b[5] = machineId[1]
+	b[6] = machineId[2]
+	// Pid, 2 bytes, specs don't specify endianness, but we use big endian.
+	b[7] = byte(processId >> 8)
+	b[8] = byte(processId)
+	// Increment, 3 bytes, big endian
+	i := atomic.AddUint32(&objectIdCounter, 1)
+	b[9] = byte(i >> 16)
+	b[10] = byte(i >> 8)
+	b[11] = byte(i)
+	return ObjectId(b[:])
+}
+
+// NewObjectIdWithTime returns a dummy ObjectId with the timestamp part filled
+// with the provided number of seconds from epoch UTC, and all other parts
+// filled with zeroes. It's not safe to insert a document with an id generated
+// by this method, it is useful only for queries to find documents with ids
+// generated before or after the specified timestamp.
+func NewObjectIdWithTime(t time.Time) ObjectId {
+	var b [12]byte
+	binary.BigEndian.PutUint32(b[:4], uint32(t.Unix()))
+	return ObjectId(string(b[:]))
+}
+
+// String returns a hex string representation of the id.
+// Example: ObjectIdHex("4d88e15b60f486e428412dc9").
+func (id ObjectId) String() string {
+	return fmt.Sprintf(`ObjectIdHex("%x")`, string(id))
+}
+
+// Hex returns a hex representation of the ObjectId.
+func (id ObjectId) Hex() string {
+	return hex.EncodeToString([]byte(id))
+}
+
+// MarshalJSON turns a bson.ObjectId into a json.Marshaller.
+func (id ObjectId) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf(`"%x"`, string(id))), nil
+}
+
+var nullBytes = []byte("null")
+
+// UnmarshalJSON turns *bson.ObjectId into a json.Unmarshaller.
+func (id *ObjectId) UnmarshalJSON(data []byte) error {
+	if len(data) > 0 && (data[0] == '{' || data[0] == 'O') {
+		var v struct {
+			Id   json.RawMessage `json:"$oid"`
+			Func struct {
+				Id json.RawMessage
+			} `json:"$oidFunc"`
+		}
+		err := jdec(data, &v)
+		if err == nil {
+			if len(v.Id) > 0 {
+				data = []byte(v.Id)
+			} else {
+				data = []byte(v.Func.Id)
+			}
+		}
+	}
+	if len(data) == 2 && data[0] == '"' && data[1] == '"' || bytes.Equal(data, nullBytes) {
+		*id = ""
+		return nil
+	}
+	if len(data) != 26 || data[0] != '"' || data[25] != '"' {
+		return fmt.Errorf("invalid ObjectId in JSON: %s", string(data))
+	}
+	var buf [12]byte
+	_, err := hex.Decode(buf[:], data[1:25])
+	if err != nil {
+		return fmt.Errorf("invalid ObjectId in JSON: %s (%s)", string(data), err)
+	}
+	*id = ObjectId(string(buf[:]))
+	return nil
+}
+
+// MarshalText turns bson.ObjectId into an encoding.TextMarshaler.
+func (id ObjectId) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("%x", string(id))), nil
+}
+
+// UnmarshalText turns *bson.ObjectId into an encoding.TextUnmarshaler.
+func (id *ObjectId) UnmarshalText(data []byte) error {
+	if len(data) == 1 && data[0] == ' ' || len(data) == 0 {
+		*id = ""
+		return nil
+	}
+	if len(data) != 24 {
+		return fmt.Errorf("invalid ObjectId: %s", data)
+	}
+	var buf [12]byte
+	_, err := hex.Decode(buf[:], data[:])
+	if err != nil {
+		return fmt.Errorf("invalid ObjectId: %s (%s)", data, err)
+	}
+	*id = ObjectId(string(buf[:]))
+	return nil
+}
+
+// Valid returns true if id is valid. A valid id must contain exactly 12 bytes.
+func (id ObjectId) Valid() bool {
+	return len(id) == 12
+}
+
+// byteSlice returns byte slice of id from start to end.
+// Calling this function with an invalid id will cause a runtime panic.
+func (id ObjectId) byteSlice(start, end int) []byte {
+	if len(id) != 12 {
+		panic(fmt.Sprintf("invalid ObjectId: %q", string(id)))
+	}
+	return []byte(string(id)[start:end])
+}
+
+// Time returns the timestamp part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id ObjectId) Time() time.Time {
+	// First 4 bytes of ObjectId is 32-bit big-endian seconds from epoch.
+	secs := int64(binary.BigEndian.Uint32(id.byteSlice(0, 4)))
+	return time.Unix(secs, 0)
+}
+
+// Machine returns the 3-byte machine id part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id ObjectId) Machine() []byte {
+	return id.byteSlice(4, 7)
+}
+
+// Pid returns the process id part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id ObjectId) Pid() uint16 {
+	return binary.BigEndian.Uint16(id.byteSlice(7, 9))
+}
+
+// Counter returns the incrementing value part of the id.
+// It's a runtime error to call this method with an invalid id.
+func (id ObjectId) Counter() int32 {
+	b := id.byteSlice(9, 12)
+	// Counter is stored as big-endian 3-byte value
+	return int32(uint32(b[0])<<16 | uint32(b[1])<<8 | uint32(b[2]))
+}
+
+// The Symbol type is similar to a string and is used in languages with a
+// distinct symbol type.
+type Symbol string
+
+// Now returns the current time with millisecond precision. MongoDB stores
+// timestamps with the same precision, so a Time returned from this method
+// will not change after a roundtrip to the database. That's the only reason
+// why this function exists. Using the time.Now function also works fine
+// otherwise.
+func Now() time.Time {
+	return time.Unix(0, time.Now().UnixNano()/1e6*1e6)
+}
+
+// MongoTimestamp is a special internal type used by MongoDB that for some
+// strange reason has its own datatype defined in BSON.
+type MongoTimestamp int64
+
+// Time returns the time part of ts which is stored with second precision.
+func (ts MongoTimestamp) Time() time.Time {
+	return time.Unix(int64(uint64(ts)>>32), 0)
+}
+
+// Counter returns the counter part of ts.
+func (ts MongoTimestamp) Counter() uint32 {
+	return uint32(ts)
+}
+
+// NewMongoTimestamp creates a timestamp using the given
+// date `t` (with second precision) and counter `c` (unique for `t`).
+//
+// Returns an error if time `t` is not between 1970-01-01T00:00:00Z
+// and 2106-02-07T06:28:15Z (inclusive).
+//
+// Note that two MongoTimestamps should never have the same (time, counter) combination:
+// the caller must ensure the counter `c` is increased if creating multiple MongoTimestamp
+// values for the same time `t` (ignoring fractions of seconds).
+func NewMongoTimestamp(t time.Time, c uint32) (MongoTimestamp, error) {
+	u := t.Unix()
+	if u < 0 || u > math.MaxUint32 {
+		return -1, errors.New("invalid value for time")
+	}
+
+	i := int64(u<<32 | int64(c))
+
+	return MongoTimestamp(i), nil
+}
+
+type orderKey int64
+
+// MaxKey is a special value that compares higher than all other possible BSON
+// values in a MongoDB database.
+var MaxKey = orderKey(1<<63 - 1)
+
+// MinKey is a special value that compares lower than all other possible BSON
+// values in a MongoDB database.
+var MinKey = orderKey(-1 << 63)
+
+type undefined struct{}
+
+// Undefined represents the undefined BSON value.
+var Undefined undefined
+
+// Binary is a representation for non-standard binary values.  Any kind should
+// work, but the following are known as of this writing:
+//
+//   0x00 - Generic. This is decoded as []byte(data), not Binary{0x00, data}.
+//   0x01 - Function (!?)
+//   0x02 - Obsolete generic.
+//   0x03 - UUID
+//   0x05 - MD5
+//   0x80 - User defined.
+//
+type Binary struct {
+	Kind byte
+	Data []byte
+}
+
+// RegEx represents a regular expression.  The Options field may contain
+// individual characters defining the way in which the pattern should be
+// applied, and must be sorted. Valid options as of this writing are 'i' for
+// case insensitive matching, 'm' for multi-line matching, 'x' for verbose
+// mode, 'l' to make \w, \W, and similar be locale-dependent, 's' for dot-all
+// mode (a '.' matches everything), and 'u' to make \w, \W, and similar match
+// unicode. The value of the Options parameter is not verified before being
+// marshaled into the BSON format.
+type RegEx struct {
+	Pattern string
+	Options string
+}
+
+// JavaScript is a type that holds JavaScript code. If Scope is non-nil, it
+// will be marshaled as a mapping from identifiers to values that may be
+// used when evaluating the provided Code.
+type JavaScript struct {
+	Code  string
+	Scope interface{}
+}
+
+// DBPointer refers to a document id in a namespace.
+//
+// This type is deprecated in the BSON specification and should not be used
+// except for backwards compatibility with ancient applications.
+type DBPointer struct {
+	Namespace string
+	Id        ObjectId
+}
+
+const initialBufferSize = 64
+
+func handleErr(err *error) {
+	if r := recover(); r != nil {
+		if _, ok := r.(runtime.Error); ok {
+			panic(r)
+		} else if _, ok := r.(externalPanic); ok {
+			panic(r)
+		} else if s, ok := r.(string); ok {
+			*err = errors.New(s)
+		} else if e, ok := r.(error); ok {
+			*err = e
+		} else {
+			panic(r)
+		}
+	}
+}
+
+// Marshal serializes the in value, which may be a map or a struct value.
+// In the case of struct values, only exported fields will be serialized,
+// and the order of serialized fields will match that of the struct itself.
+// The lowercased field name is used as the key for each exported field,
+// but this behavior may be changed using the respective field tag.
+// The tag may also contain flags to tweak the marshalling behavior for
+// the field. The tag formats accepted are:
+//
+//     "[<key>][,<flag1>[,<flag2>]]"
+//
+//     `(...) bson:"[<key>][,<flag1>[,<flag2>]]" (...)`
+//
+// The following flags are currently supported:
+//
+//     omitempty  Only include the field if it's not set to the zero
+//                value for the type or to empty slices or maps.
+//
+//     minsize    Marshal an int64 value as an int32, if that's feasible
+//                while preserving the numeric value.
+//
+//     inline     Inline the field, which must be a struct or a map,
+//                causing all of its fields or keys to be processed as if
+//                they were part of the outer struct. For maps, keys must
+//                not conflict with the bson keys of other struct fields.
+//
+// Some examples:
+//
+//     type T struct {
+//         A bool
+//         B int    "myb"
+//         C string "myc,omitempty"
+//         D string `bson:",omitempty" json:"jsonkey"`
+//         E int64  ",minsize"
+//         F int64  "myf,omitempty,minsize"
+//     }
+//
+func Marshal(in interface{}) (out []byte, err error) {
+	return MarshalBuffer(in, make([]byte, 0, initialBufferSize))
+}
+
+// MarshalBuffer behaves the same way as Marshal, except that instead of
+// allocating a new byte slice it tries to use the received byte slice and
+// only allocates more memory if necessary to fit the marshaled value.
+func MarshalBuffer(in interface{}, buf []byte) (out []byte, err error) {
+	defer handleErr(&err)
+	e := &encoder{buf}
+	e.addDoc(reflect.ValueOf(in))
+	return e.out, nil
+}
+
+// Unmarshal deserializes data from in into the out value.  The out value
+// must be a map, a pointer to a struct, or a pointer to a bson.D value.
+// In the case of struct values, only exported fields will be deserialized.
+// The lowercased field name is used as the key for each exported field,
+// but this behavior may be changed using the respective field tag.
+// The tag may also contain flags to tweak the marshalling behavior for
+// the field. The tag formats accepted are:
+//
+//     "[<key>][,<flag1>[,<flag2>]]"
+//
+//     `(...) bson:"[<key>][,<flag1>[,<flag2>]]" (...)`
+//
+// The following flags are currently supported during unmarshal (see the
+// Marshal method for other flags):
+//
+//     inline     Inline the field, which must be a struct or a map.
+//                Inlined structs are handled as if its fields were part
+//                of the outer struct. An inlined map causes keys that do
+//                not match any other struct field to be inserted in the
+//                map rather than being discarded as usual.
+//
+// The target field or element types of out may not necessarily match
+// the BSON values of the provided data.  The following conversions are
+// made automatically:
+//
+// - Numeric types are converted if at least the integer part of the
+//   value would be preserved correctly
+// - Bools are converted to numeric types as 1 or 0
+// - Numeric types are converted to bools as true if not 0 or false otherwise
+// - Binary and string BSON data is converted to a string, array or byte slice
+//
+// If the value would not fit the type and cannot be converted, it's
+// silently skipped.
+//
+// Pointer values are initialized when necessary.
+func Unmarshal(in []byte, out interface{}) (err error) {
+	if raw, ok := out.(*Raw); ok {
+		raw.Kind = 3
+		raw.Data = in
+		return nil
+	}
+	defer handleErr(&err)
+	v := reflect.ValueOf(out)
+	switch v.Kind() {
+	case reflect.Ptr:
+		fallthrough
+	case reflect.Map:
+		d := newDecoder(in)
+		d.readDocTo(v)
+		if d.i < len(d.in) {
+			return errors.New("document is corrupted")
+		}
+	case reflect.Struct:
+		return errors.New("unmarshal can't deal with struct values. Use a pointer")
+	default:
+		return errors.New("unmarshal needs a map or a pointer to a struct")
+	}
+	return nil
+}
+
+// Unmarshal deserializes raw into the out value.  If the out value type
+// is not compatible with raw, a *bson.TypeError is returned.
+//
+// See the Unmarshal function documentation for more details on the
+// unmarshalling process.
+func (raw Raw) Unmarshal(out interface{}) (err error) {
+	defer handleErr(&err)
+	v := reflect.ValueOf(out)
+	switch v.Kind() {
+	case reflect.Ptr:
+		v = v.Elem()
+		fallthrough
+	case reflect.Map:
+		d := newDecoder(raw.Data)
+		good := d.readElemTo(v, raw.Kind)
+		if !good {
+			return &TypeError{v.Type(), raw.Kind}
+		}
+	case reflect.Struct:
+		return errors.New("raw Unmarshal can't deal with struct values. Use a pointer")
+	default:
+		return errors.New("raw Unmarshal needs a map or a valid pointer")
+	}
+	return nil
+}
+
+// TypeError store details for type error occuring
+// during unmarshaling
+type TypeError struct {
+	Type reflect.Type
+	Kind byte
+}
+
+func (e *TypeError) Error() string {
+	return fmt.Sprintf("BSON kind 0x%02x isn't compatible with type %s", e.Kind, e.Type.String())
+}
+
+// --------------------------------------------------------------------------
+// Maintain a mapping of keys to structure field indexes
+
+type structInfo struct {
+	FieldsMap  map[string]fieldInfo
+	FieldsList []fieldInfo
+	InlineMap  int
+	Zero       reflect.Value
+}
+
+type fieldInfo struct {
+	Key       string
+	Num       int
+	OmitEmpty bool
+	MinSize   bool
+	Inline    []int
+}
+
+var structMap = make(map[reflect.Type]*structInfo)
+var structMapMutex sync.RWMutex
+
+type externalPanic string
+
+func (e externalPanic) String() string {
+	return string(e)
+}
+
+func getStructInfo(st reflect.Type) (*structInfo, error) {
+	structMapMutex.RLock()
+	sinfo, found := structMap[st]
+	structMapMutex.RUnlock()
+	if found {
+		return sinfo, nil
+	}
+	n := st.NumField()
+	fieldsMap := make(map[string]fieldInfo)
+	fieldsList := make([]fieldInfo, 0, n)
+	inlineMap := -1
+	for i := 0; i != n; i++ {
+		field := st.Field(i)
+		if field.PkgPath != "" && !field.Anonymous {
+			continue // Private field
+		}
+
+		info := fieldInfo{Num: i}
+
+		tag := field.Tag.Get("bson")
+
+		// Fall-back to JSON struct tag, if feature flag is set.
+		if tag == "" && useJSONTagFallback {
+			tag = field.Tag.Get("json")
+		}
+
+		// If there's no bson/json tag available.
+		if tag == "" {
+			// If there's no tag, and also no tag: value splits (i.e. no colon)
+			// then assume the entire tag is the value
+			if strings.Index(string(field.Tag), ":") < 0 {
+				tag = string(field.Tag)
+			}
+		}
+
+		if tag == "-" {
+			continue
+		}
+
+		inline := false
+		fields := strings.Split(tag, ",")
+		if len(fields) > 1 {
+			for _, flag := range fields[1:] {
+				switch flag {
+				case "omitempty":
+					info.OmitEmpty = true
+				case "minsize":
+					info.MinSize = true
+				case "inline":
+					inline = true
+				default:
+					msg := fmt.Sprintf("Unsupported flag %q in tag %q of type %s", flag, tag, st)
+					panic(externalPanic(msg))
+				}
+			}
+			tag = fields[0]
+		}
+
+		if inline {
+			switch field.Type.Kind() {
+			case reflect.Map:
+				if inlineMap >= 0 {
+					return nil, errors.New("Multiple ,inline maps in struct " + st.String())
+				}
+				if field.Type.Key() != reflect.TypeOf("") {
+					return nil, errors.New("Option ,inline needs a map with string keys in struct " + st.String())
+				}
+				inlineMap = info.Num
+			case reflect.Ptr:
+				// allow only pointer to struct
+				if kind := field.Type.Elem().Kind(); kind != reflect.Struct {
+					return nil, errors.New("Option ,inline allows a pointer only to a struct, was given pointer to " + kind.String())
+				}
+
+				field.Type = field.Type.Elem()
+				fallthrough
+			case reflect.Struct:
+				sinfo, err := getStructInfo(field.Type)
+				if err != nil {
+					return nil, err
+				}
+				for _, finfo := range sinfo.FieldsList {
+					if _, found := fieldsMap[finfo.Key]; found {
+						msg := "Duplicated key '" + finfo.Key + "' in struct " + st.String()
+						return nil, errors.New(msg)
+					}
+					if finfo.Inline == nil {
+						finfo.Inline = []int{i, finfo.Num}
+					} else {
+						finfo.Inline = append([]int{i}, finfo.Inline...)
+					}
+					fieldsMap[finfo.Key] = finfo
+					fieldsList = append(fieldsList, finfo)
+				}
+			default:
+				panic("Option ,inline needs a struct value or a pointer to a struct or map field")
+			}
+			continue
+		}
+
+		if tag != "" {
+			info.Key = tag
+		} else {
+			info.Key = strings.ToLower(field.Name)
+		}
+
+		if _, found = fieldsMap[info.Key]; found {
+			msg := "Duplicated key '" + info.Key + "' in struct " + st.String()
+			return nil, errors.New(msg)
+		}
+
+		fieldsList = append(fieldsList, info)
+		fieldsMap[info.Key] = info
+	}
+	sinfo = &structInfo{
+		fieldsMap,
+		fieldsList,
+		inlineMap,
+		reflect.New(st).Elem(),
+	}
+	structMapMutex.Lock()
+	structMap[st] = sinfo
+	structMapMutex.Unlock()
+	return sinfo, nil
+}