bunch of changes

internal/ast/ast.go

@@ -38,13 +38,13 @@ func (p *Program) TokenLiteral() string {
 }
 
 func (p *Program) String() string {
-	var out bytes.Buffer
+	var s strings.Builder
 
-	for _, s := range p.Statements {
-		out.WriteString(s.String())
+	for _, stmt := range p.Statements {
+		s.WriteString(fmt.Sprintf("%s\n", stmt.String()))
 	}
 
-	return out.String()
+	return s.String()
 }
 
 type ReturnStatement struct {