Add a go_test to //build_tests

I wanted to provide an example for students to write tests. This
should hopefully get them started.

Signed-off-by: Philipp Schrader <philipp.schrader@gmail.com>
Change-Id: I5b5e5509075cc6e30f5138b3a213c8966fd15763
diff --git a/build_tests/hello.go b/build_tests/hello.go
index d2c4e91..2c741a8 100644
--- a/build_tests/hello.go
+++ b/build_tests/hello.go
@@ -1,7 +1,11 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+
+	"github.com/frc971/971-Robot-Code/build_tests/go_greeter"
+)
 
 func main() {
-	fmt.Println("Hello world")
+	fmt.Println(go_greeter.Greet("world"))
 }