feat: add go-bench command

go/go.justfile

@@ -6,3 +6,6 @@
 
 @bench-go: build-go
     hyperfine './go/a < ./input.txt'
+
+@go-bench:
+    cd go && go test -bench=.

go/main_test.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"testing"
+)
+
+const N int = 100_000_000
+
+var num int = 10
+
+func BenchmarkAdd1(b *testing.B) {
+	for i := 0; i < N; i++ {
+		_ = num * num
+	}
+}