diff --git a/runtime/Go/antlr/v4/lexer.go b/runtime/Go/antlr/v4/lexer.go
index 6533f05164..0d81c9d6ac 100644
--- a/runtime/Go/antlr/v4/lexer.go
+++ b/runtime/Go/antlr/v4/lexer.go
@@ -118,7 +118,7 @@ const (
 	LexerMaxCharValue        = 0x10FFFF
 )
 
-func (b *BaseLexer) reset() {
+func (b *BaseLexer) Reset() {
 	// wack Lexer state variables
 	if b.input != nil {
 		b.input.Seek(0) // rewind the input
@@ -280,7 +280,7 @@ func (b *BaseLexer) inputStream() CharStream {
 func (b *BaseLexer) SetInputStream(input CharStream) {
 	b.input = nil
 	b.tokenFactorySourcePair = &TokenSourceCharStreamPair{b, b.input}
-	b.reset()
+	b.Reset()
 	b.input = input
 	b.tokenFactorySourcePair = &TokenSourceCharStreamPair{b, b.input}
 }
diff --git a/runtime/Go/antlr/v4/testing_api_test.go b/runtime/Go/antlr/v4/testing_api_test.go
new file mode 100644
index 0000000000..eed3ce34be
--- /dev/null
+++ b/runtime/Go/antlr/v4/testing_api_test.go
@@ -0,0 +1,30 @@
+package antlr
+
+import (
+	"testing"
+)
+
+func next(t *testing.T, lexer *LexerB, want string) {
+	var token = lexer.NextToken()
+	var got = token.String()
+	if got != want {
+		t.Errorf("got %q, wanted %q", got, want)
+	}
+}
+
+func TestString(t *testing.T) {
+	str := NewInputStream("a b c 1 2 3")
+	lexer := NewLexerB(str)
+	next(t, lexer, "[@-1,0:0='a',<1>,1:0]")
+	next(t, lexer, "[@-1,1:1=' ',<7>,1:1]")
+	next(t, lexer, "[@-1,2:2='b',<1>,1:2]")
+	next(t, lexer, "[@-1,3:3=' ',<7>,1:3]")
+	next(t, lexer, "[@-1,4:4='c',<1>,1:4]")
+	next(t, lexer, "[@-1,5:5=' ',<7>,1:5]")
+	next(t, lexer, "[@-1,6:6='1',<2>,1:6]")
+	next(t, lexer, "[@-1,7:7=' ',<7>,1:7]")
+	next(t, lexer, "[@-1,8:8='2',<2>,1:8]")
+	next(t, lexer, "[@-1,9:9=' ',<7>,1:9]")
+	next(t, lexer, "[@-1,10:10='3',<2>,1:10]")
+	next(t, lexer, "[@-1,11:10='<EOF>',<-1>,1:11]")
+}
diff --git a/runtime/Go/antlr/v4/token.go b/runtime/Go/antlr/v4/token.go
index f73b06bc6a..a77b941427 100644
--- a/runtime/Go/antlr/v4/token.go
+++ b/runtime/Go/antlr/v4/token.go
@@ -35,6 +35,8 @@ type Token interface {
 
 	GetTokenSource() TokenSource
 	GetInputStream() CharStream
+
+	String() string
 }
 
 type BaseToken struct {
diff --git a/runtime/Go/antlr/v4/tree.go b/runtime/Go/antlr/v4/tree.go
index 85b4f137b5..756f3092e6 100644
--- a/runtime/Go/antlr/v4/tree.go
+++ b/runtime/Go/antlr/v4/tree.go
@@ -250,4 +250,62 @@ func (p *ParseTreeWalker) ExitRule(listener ParseTreeListener, r RuleNode) {
 	listener.ExitEveryRule(ctx)
 }
 
+//goland:noinspection GoUnusedGlobalVariable
 var ParseTreeWalkerDefault = NewParseTreeWalker()
+
+type IterativeParseTreeWalker struct {
+	*ParseTreeWalker
+}
+
+func NewIterativeParseTreeWalker() *IterativeParseTreeWalker {
+	return new(IterativeParseTreeWalker)
+}
+
+func (i *IterativeParseTreeWalker) Walk(listener ParseTreeListener, t Tree) {
+	var stack []Tree
+	var indexStack []int
+	currentNode := t
+	currentIndex := 0
+
+	for currentNode != nil {
+		// pre-order visit
+		switch tt := currentNode.(type) {
+		case ErrorNode:
+			listener.VisitErrorNode(tt)
+		case TerminalNode:
+			listener.VisitTerminal(tt)
+		default:
+			i.EnterRule(listener, currentNode.(RuleNode))
+		}
+		// Move down to first child, if exists
+		if currentNode.GetChildCount() > 0 {
+			stack = append(stack, currentNode)
+			indexStack = append(indexStack, currentIndex)
+			currentIndex = 0
+			currentNode = currentNode.GetChild(0)
+			continue
+		}
+
+		for {
+			// post-order visit
+			if ruleNode, ok := currentNode.(RuleNode); ok {
+				i.ExitRule(listener, ruleNode)
+			}
+			// No parent, so no siblings
+			if len(stack) == 0 {
+				currentNode = nil
+				currentIndex = 0
+				break
+			}
+			// Move to next sibling if possible
+			currentIndex++
+			if stack[len(stack)-1].GetChildCount() > currentIndex {
+				currentNode = stack[len(stack)-1].GetChild(currentIndex)
+				break
+			}
+			// No next, sibling, so move up
+			currentNode, stack = stack[len(stack)-1], stack[:len(stack)-1]
+			currentIndex, indexStack = indexStack[len(indexStack)-1], indexStack[:len(indexStack)-1]
+		}
+	}
+}