ddtrace/tracer: add freebsd osinfo support (DataDog#766)

ddtrace/tracer/osinfo_default.go

@@ -3,7 +3,7 @@
 // This product includes software developed at Datadog (https://www.datadoghq.com/).
 // Copyright 2016-2020 Datadog, Inc.
 
-// +build !windows,!linux,!darwin
+// +build !windows,!linux,!darwin,!freebsd
 
 package tracer
 

ddtrace/tracer/osinfo_freebsd.go

@@ -0,0 +1,24 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2016-2020 Datadog, Inc.
+
+package tracer
+
+import (
+	"os/exec"
+	"runtime"
+	"strings"
+)
+
+func osName() string {
+	return runtime.GOOS
+}
+
+func osVersion() string {
+	out, err := exec.Command("uname", "-r").Output()
+	if err != nil {
+		return unknown
+	}
+	return strings.Split(string(out), "-")[0]
+}