Add all the files from the interpreter repo

Signed-off-by: jmug <u.g.a.mariano@gmail.com>

pkg/ast/return.go

@@ -0,0 +1,26 @@
+package ast
+
+import (
+	"bytes"
+
+	"code.jmug.me/jmug/interpreter-in-go/pkg/token"
+)
+
+type ReturnStatement struct {
+	Token       token.Token // TODO: This is a little redundant, figure out if I can get rid of it.
+	ReturnValue Expression
+}
+
+func (rs *ReturnStatement) statementNode() {}
+func (rs *ReturnStatement) TokenLiteral() string {
+	return rs.Token.Literal
+}
+func (rs *ReturnStatement) String() string {
+	var out bytes.Buffer
+	out.WriteString(rs.TokenLiteral())
+	if rs.ReturnValue != nil {
+		out.WriteString(" " + rs.ReturnValue.String())
+	}
+	out.WriteString(";")
+	return out.String()
+}