Package pidfile implements pidfile creation. On Linux and Darwin, this package uses flock to take an exclusive lock of the pidfile. If another process tries to lock the file, an error will be returned. If the previous process dies and does not unlock the file or delete it, the operating system cleans up the lock automatically and this package will adopt the file and lock it. This package relies on the operating system to handle the locking. Some filesystems, such as NFS, may not implement flock in a reliable way. You should not use this package on such operating systems. The file locking is only an advisory. If the file is manually opened by a call to os.Open, the file will still open normally.