Cherry pick v1.7 into master

vendor/github.com/mitchellh/mapstructure/decode_hooks.go

@@ -2,6 +2,8 @@ package mapstructure
 
 import (
 	"errors"
+	"fmt"
+	"net"
 	"reflect"
 	"strconv"
 	"strings"
@@ -115,6 +117,69 @@ func StringToTimeDurationHookFunc() DecodeHookFunc {
 	}
 }
 
+// StringToIPHookFunc returns a DecodeHookFunc that converts
+// strings to net.IP
+func StringToIPHookFunc() DecodeHookFunc {
+	return func(
+		f reflect.Type,
+		t reflect.Type,
+		data interface{}) (interface{}, error) {
+		if f.Kind() != reflect.String {
+			return data, nil
+		}
+		if t != reflect.TypeOf(net.IP{}) {
+			return data, nil
+		}
+
+		// Convert it by parsing
+		ip := net.ParseIP(data.(string))
+		if ip == nil {
+			return net.IP{}, fmt.Errorf("failed parsing ip %v", data)
+		}
+
+		return ip, nil
+	}
+}
+
+// StringToIPNetHookFunc returns a DecodeHookFunc that converts
+// strings to net.IPNet
+func StringToIPNetHookFunc() DecodeHookFunc {
+	return func(
+		f reflect.Type,
+		t reflect.Type,
+		data interface{}) (interface{}, error) {
+		if f.Kind() != reflect.String {
+			return data, nil
+		}
+		if t != reflect.TypeOf(net.IPNet{}) {
+			return data, nil
+		}
+
+		// Convert it by parsing
+		_, net, err := net.ParseCIDR(data.(string))
+		return net, err
+	}
+}
+
+// StringToTimeHookFunc returns a DecodeHookFunc that converts
+// strings to time.Time.
+func StringToTimeHookFunc(layout string) DecodeHookFunc {
+	return func(
+		f reflect.Type,
+		t reflect.Type,
+		data interface{}) (interface{}, error) {
+		if f.Kind() != reflect.String {
+			return data, nil
+		}
+		if t != reflect.TypeOf(time.Time{}) {
+			return data, nil
+		}
+
+		// Convert it by parsing
+		return time.Parse(layout, data.(string))
+	}
+}
+
 // WeaklyTypedHook is a DecodeHookFunc which adds support for weak typing to
 // the decoder.
 //