diff --git a/go/fn/errors.go b/go/fn/errors.go
index 8c80a412a..d2b322701 100644
--- a/go/fn/errors.go
+++ b/go/fn/errors.go
@@ -18,6 +18,8 @@ import (
 	"fmt"
 	"log"
 	"strings"
+
+	"github.com/GoogleContainerTools/kpt-functions-sdk/go/fn/internal"
 )
 
 // ErrMissingFnConfig raises error if a required functionConfig is missing.
@@ -40,9 +42,12 @@ func (e *ErrOpOrDie) Error() string {
 
 func handleOptOrDieErr() {
 	if v := recover(); v != nil {
-		if e, ok := v.(ErrOpOrDie); ok {
-			log.Fatalf(e.Error())
-		} else {
+		switch v.(type) {
+		case ErrOpOrDie:
+			log.Fatalf(v.(*ErrOpOrDie).Error())
+		case internal.ErrEqualSelector:
+			log.Fatalf(v.(*internal.ErrEqualSelector).Error())
+		default:
 			panic(v)
 		}
 	}
diff --git a/go/fn/examples/example_read_field_test.go b/go/fn/examples/example_read_field_test.go
index 46a50a03b..bee226855 100644
--- a/go/fn/examples/example_read_field_test.go
+++ b/go/fn/examples/example_read_field_test.go
@@ -30,10 +30,13 @@ func Example_aReadField() {
 
 func readField(rl *fn.ResourceList) error {
 	for _, obj := range rl.Items {
-		if obj.GetAPIVersion() == "apps/v1" && obj.GetKind() == "Deployment" {
+		switch{
+		case obj.IsGVK("apps/v1", "Deployment"):
 			var replicas int
 			obj.GetOrDie(&replicas, "spec", "replicas")
-			fn.Logf("replicas is %v\n", replicas)
+		case obj.IsGVK("rbac.authorization.k8s.io/v1", "ClusterRoleBinding"):
+			var namespace string
+			obj.GetOrDie(&namespace, "subjects", "kind=ServiceAccount", "namespace")
 		}
 	}
 	return nil
diff --git a/go/fn/examples/example_set_field_test.go b/go/fn/examples/example_set_field_test.go
index 9bd27f4cf..8bf16c54f 100644
--- a/go/fn/examples/example_set_field_test.go
+++ b/go/fn/examples/example_set_field_test.go
@@ -30,9 +30,13 @@ func Example_cSetField() {
 
 func setField(rl *fn.ResourceList) error {
 	for _, obj := range rl.Items {
-		if obj.GetAPIVersion() == "apps/v1" && obj.GetKind() == "Deployment" {
+		switch{
+		case obj.IsGVK("apps/v1", "Deployment"):
 			replicas := 10
 			obj.SetOrDie(&replicas, "spec", "replicas")
+		case obj.IsGVK("rbac.authorization.k8s.io/v1", "ClusterRoleBinding"):
+			namespace := "test"
+			obj.SetOrDie(&namespace, "subjects", "kind=ServiceAccount", "namespace")
 		}
 	}
 	return nil
diff --git a/go/fn/internal/errors.go b/go/fn/internal/errors.go
new file mode 100644
index 000000000..2785dfa5f
--- /dev/null
+++ b/go/fn/internal/errors.go
@@ -0,0 +1,16 @@
+package internal
+
+import (
+	"fmt"
+)
+
+// ErrOpOrDie raises if the KubeObject operation panics.
+type ErrEqualSelector struct {
+	field string
+	expected string
+	actual string
+}
+
+func (e *ErrEqualSelector) Error() string {
+	return fmt.Sprintf("invalid selector syntax: expect %v, got %v ", e.expected, e.actual)
+}
diff --git a/go/fn/internal/maphelpers.go b/go/fn/internal/maphelpers.go
index 124998c02..258151db9 100644
--- a/go/fn/internal/maphelpers.go
+++ b/go/fn/internal/maphelpers.go
@@ -16,13 +16,15 @@ package internal
 
 import (
 	"fmt"
+	"strings"
 )
 
 func (o *MapVariant) GetNestedValue(fields ...string) (variant, bool, error) {
-	current := o
+	var current variant
+	current = o
 	n := len(fields)
 	for i := 0; i < n; i++ {
-		entry, found := current.getVariant(fields[i])
+		entry, found := current.(*MapVariant).getVariant(fields[i])
 		if !found {
 			return nil, found, nil
 		}
@@ -30,26 +32,67 @@ func (o *MapVariant) GetNestedValue(fields ...string) (variant, bool, error) {
 		if i == n-1 {
 			return entry, true, nil
 		}
-		entryM, ok := entry.(*MapVariant)
-		if !ok {
+		switch entry.(type){
+		case *MapVariant:
+			current, _ = entry.(*MapVariant)
+		case *sliceVariant:
+			if i+1 < n && IsEqualSelector(fields[i+1]) {
+				foundMapVar, err := entry.(*sliceVariant).GetSliceElementBySelector(fields[i+1])
+				if err != nil {
+					return nil, found, err
+				}
+				if foundMapVar != nil {
+					current = foundMapVar
+					i += 1
+				} else {
+					return nil, false, nil
+				}
+			} else {
+				return nil, found, fmt.Errorf("wrong type, got: %T", entry)
+			}
+		default:
 			return nil, found, fmt.Errorf("wrong type, got: %T", entry)
 		}
-		current = entryM
 	}
 	return nil, false, fmt.Errorf("unexpected code reached")
 }
 
 func (o *MapVariant) SetNestedValue(val variant, fields ...string) error {
-	current := o
+	var current variant
+	current = o
 	n := len(fields)
 	var err error
 	for i := 0; i < n; i++ {
 		if i == n-1 {
-			current.set(fields[i], val)
+			current.(*MapVariant).set(fields[i], val)
 		} else {
-			current, _, err = current.getMap(fields[i], true)
-			if err != nil {
-				return err
+			entry, found := current.(*MapVariant).getVariant(fields[i])
+			if !found{
+				return fmt.Errorf("fields not exist %v", strings.Join(fields, "."))
+			}
+			switch entry.(type){
+			case *sliceVariant:
+				if i+1 < n && IsEqualSelector(fields[i+1]) {
+					mapVar, err := entry.(*sliceVariant).GetSliceElementBySelector(fields[i+1])
+					if err != nil {
+						return err
+					}
+					if mapVar == nil {
+						valueNode := buildMappingNode()
+						valueVariant := &MapVariant{node: valueNode}
+						entry.(*sliceVariant).Add(valueVariant)
+						current = valueVariant
+						return fmt.Errorf("no matching element in selector %v", fields[i+1])
+					} else {
+						current = mapVar
+						i += 1
+					}
+				}
+			default: // MapVariant or not exist
+				current, _, err = current.(*MapVariant).getMap(fields[i], true)
+				if err != nil {
+					return err
+				}
 			}
 		}
 	}
diff --git a/go/fn/internal/selector.go b/go/fn/internal/selector.go
new file mode 100644
index 000000000..c2f5cf898
--- /dev/null
+++ b/go/fn/internal/selector.go
@@ -0,0 +1,37 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package internal
+
+import (
+	"strings"
+)
+
+const equalDelimiter = "="
+
+func IsEqualSelector(field string) bool{
+	if strings.Contains(field, equalDelimiter) {
+		return true
+	}
+	// TODO: extend and support multi "equal" syntax. e.g. `kind=Project,name=kit`
+	return false
+}
+
+func GetEqualSelector(field string) (string, string){
+	segments := strings.Split(field, equalDelimiter)
+	if len(segments) != 2 {
+		panic(ErrEqualSelector{expected: "YOUR_KEY=YOUR_VALUE", actual: field})
+	}
+	return segments[0], segments[1]
+}
+
diff --git a/go/fn/internal/slice.go b/go/fn/internal/slice.go
index a7b5e1180..59f17c747 100644
--- a/go/fn/internal/slice.go
+++ b/go/fn/internal/slice.go
@@ -49,3 +49,24 @@ func (v *sliceVariant) Objects() ([]*MapVariant, error) {
 func (v *sliceVariant) Add(node variant) {
 	v.node.Content = append(v.node.Content, node.Node())
 }
+
+func (o *sliceVariant) GetSliceElementBySelector(field string) (*MapVariant, error) {
+	key, expected := GetEqualSelector(field)
+	elements, err := o.Objects()
+	if err != nil {
+		return nil, err
+	}
+	for _, mapElement := range elements {
+		actual, found, err := mapElement.GetNestedString(key)
+		if !found {
+			continue
+		}
+		if err != nil {
+			return nil, err
+		}
+		if actual == expected {
+			return mapElement, nil
+		}
+	}
+	return nil, nil
+}