Add a lot of documentation

copy_both_response.go

@@ -13,8 +13,11 @@ type CopyBothResponse struct {
 	ColumnFormatCodes []uint16
 }
 
+// Backend identifies this message as sendable by the PostgreSQL backend.
 func (*CopyBothResponse) Backend() {}
 
+// Decode decodes src into dst. src must contain the complete message with the exception of the initial 1 byte message
+// type identifier and 4 byte message length.
 func (dst *CopyBothResponse) Decode(src []byte) error {
 	buf := bytes.NewBuffer(src)
 
@@ -39,6 +42,7 @@ func (dst *CopyBothResponse) Decode(src []byte) error {
 	return nil
 }
 
+// Encode encodes src into dst. dst will include the 1 byte message type identifier and the 4 byte message length.
 func (src *CopyBothResponse) Encode(dst []byte) []byte {
 	dst = append(dst, 'W')
 	sp := len(dst)
@@ -54,6 +58,7 @@ func (src *CopyBothResponse) Encode(dst []byte) []byte {
 	return dst
 }
 
+// MarshalJSON implements encoding/json.Marshaler.
 func (src *CopyBothResponse) MarshalJSON() ([]byte, error) {
 	return json.Marshal(struct {
 		Type              string