go/src/cmd/go/internal/lockedfile/internal/filelock/filelock.go

type File …

// Lock places an advisory write lock on the file, blocking until it can be
// locked.
//
// If Lock returns nil, no other process will be able to place a read or write
// lock on the file until this process exits, closes f, or calls Unlock on it.
//
// If f's descriptor is already read- or write-locked, the behavior of Lock is
// unspecified.
//
// Closing the file may or may not release the lock promptly. Callers should
// ensure that Unlock is always called when Lock succeeds.
func Lock(f File) error { … }

// RLock places an advisory read lock on the file, blocking until it can be locked.
//
// If RLock returns nil, no other process will be able to place a write lock on
// the file until this process exits, closes f, or calls Unlock on it.
//
// If f is already read- or write-locked, the behavior of RLock is unspecified.
//
// Closing the file may or may not release the lock promptly. Callers should
// ensure that Unlock is always called if RLock succeeds.
func RLock(f File) error { … }

// Unlock removes an advisory lock placed on f by this process.
//
// The caller must not attempt to unlock a file that is not locked.
func Unlock(f File) error { … }

// String returns the name of the function corresponding to lt
// (Lock, RLock, or Unlock).
func (lt lockType) String() string { … }

// IsNotSupported returns a boolean indicating whether the error is known to
// report that a function is not supported (possibly for a specific input).
// It is satisfied by errors.ErrUnsupported as well as some syscall errors.
func IsNotSupported(err error) bool { … }