Add UnmarshalJSON to a few types

pgtype/int4.go

@@ -3,6 +3,7 @@ package pgtype
 import (
 	"database/sql/driver"
 	"encoding/binary"
+	"encoding/json"
 	"math"
 	"strconv"
 
@@ -198,3 +199,15 @@ func (src *Int4) MarshalJSON() ([]byte, error) {
 
 	return nil, errBadStatus
 }
+
+func (dst *Int4) UnmarshalJSON(b []byte) error {
+	var n int32
+	err := json.Unmarshal(b, &n)
+	if err != nil {
+		return err
+	}
+
+	*dst = Int4{Int: n, Status: Present}
+
+	return nil
+}

pgtype/text.go

@@ -149,3 +149,15 @@ func (src *Text) MarshalJSON() ([]byte, error) {
 
 	return nil, errBadStatus
 }
+
+func (dst *Text) UnmarshalJSON(b []byte) error {
+	var s string
+	err := json.Unmarshal(b, &s)
+	if err != nil {
+		return err
+	}
+
+	*dst = Text{String: s, Status: Present}
+
+	return nil
+}

pgtype/varchar.go

@@ -52,3 +52,7 @@ func (src *Varchar) Value() (driver.Value, error) {
 func (src *Varchar) MarshalJSON() ([]byte, error) {
 	return (*Text)(src).MarshalJSON()
 }
+
+func (dst *Varchar) UnmarshalJSON(b []byte) error {
+	return (*Text)(dst).UnmarshalJSON(b)
+}