Adds makefile to go interpreter (#14)

.gitignore

@@ -66,3 +66,4 @@ go.work
 *.exe
 *.out
 *.app
+go/bin/*

go/makefile

@@ -0,0 +1,12 @@
+run:
+	@go run main.go
+
+build:
+	@mkdir -p bin
+	@go build -o bin/monkey main.go
+	@echo "Build complete"
+	@echo "Run ./bin/monkey to start the program"
+	@echo "Or add the bin directory to your PATH"
+
+test:
+	@go test -v ./...

go/repl/repl.go

@@ -9,7 +9,12 @@ import (
 	"github.com/abasnfarah/monkey-interpreter/go/token"
 )
 
-const PROMPT = ">> "
+const (
+	PROMPT       = ">> "
+	HELP_MESSAGE = "help - show this help message\n" + "exit - exit the repl\n"
+	HELP         = "help"
+	EXIT         = "exit"
+)
 
 func Start(in io.Reader, out io.Writer) {
 	scanner := bufio.NewScanner(in)
@@ -22,10 +27,15 @@ func Start(in io.Reader, out io.Writer) {
 		}
 
 		line := scanner.Text()
-		if line == "exit" {
+		if line == EXIT {
 			return
 		}
 
+		if line == HELP || line == "h" || line == "" {
+			fmt.Fprint(out, HELP_MESSAGE)
+			continue
+		}
+
 		l := lexer.New(line)
 
 		fmt.Fprintf(out, "%+v\n", l)