You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: userns_linux.go
    path of file: ./repos/teller/vendor/github.com/containerd/containerd/sys
    
    the code of the file until where you have to start completion: /*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses
    
func RunningInUserNS() bool {
	nsOnce.Do(func() {
		file, err := os.Open("/proc/self/uid_map")
		if err != nil {
			// This kernel-provided file only exists if user namespaces are supported
			return
		}
		defer file.Close()

		buf := bufio.NewReader(file)
		l, _, err := buf.ReadLine()
		if err != nil {
			return
		}

		line := string(l)
		var a, b, c int64
		fmt.Sscanf(line, "%d %d %d", &a, &b, &c)

		/*
		 * We assume we are in the initial user namespace if we have a full
		 * range - 4294967295 uids starting at uid 0.
		 */
		if a == 0 && b == 0 && c == 4294967295 {
			return
		}
		inUserNS = true
	})
	return inUserNS
}