Introduce pgproto3 package

pgproto3 will wrap the message encoding and decoding for the PostgreSQL
frontend/backend protocol version 3.

parse_complete.go

@@ -0,0 +1,29 @@
+package pgproto3
+
+import (
+	"encoding/json"
+)
+
+type ParseComplete struct{}
+
+func (*ParseComplete) Backend() {}
+
+func (dst *ParseComplete) UnmarshalBinary(src []byte) error {
+	if len(src) != 0 {
+		return &invalidMessageLenErr{messageType: "ParseComplete", expectedLen: 0, actualLen: len(src)}
+	}
+
+	return nil
+}
+
+func (src *ParseComplete) MarshalBinary() ([]byte, error) {
+	return []byte{'1', 0, 0, 0, 4}, nil
+}
+
+func (src *ParseComplete) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type string
+	}{
+		Type: "ParseComplete",
+	})
+}