type Lock will be better
Lock.New() for initializing Lock
Directory structure - extensions main directory and then lock directory

Rename "retries"

rename retryDelay

fLock

Not used.

Not used.

Add internal sync.Mutex called mu.

Add these lines:

c.mu.Lock()
defer c.mu.Unlock()

Change (c CrossPlatLock) to use a pointer

Have this return a pointer

Let's get rid of lockFileName, use a default defined in a constructor.

Let's use this signature:

type Option func(l *Lock)

func WithRetries(n int) Option{
return func(l *Lock) {
l.retries = n
}
}

func New(options ...Option) (*Lock, error) {
l := &Lock{
...
}
for _, o := range options {
o(l)
}
...
return l, nil
}

Add defer c.mu.Unlock()

error text must start with lower case letter

var
(
count int
prevProc, tag, proc string
)
)

All in one line and call it s instead of ele

You need to add default value for retries and retryDelay.

Public requires a comment. I'd put:

// WithRetryDelay changes the default delay from [delay] to t.

Public requires a comment. I'd put:

// WithRetries changes the default number of retries from [retries] to n. Negative values panic()

Also, add panic on negative values.

lockFileName can be just "p".

// New creates a Lock for a lock file at "p". If "p" doesn't exist, it will be created when using. Lock().
func New(p string options ...Option) (*Lock, error)

for i := 0; i < l.retries; i++ {
...

Add two tests:

One tests all the conditions of Lock().
Another tests all the conditions of Unlock()

• flock.Unlock() has error
• Lockfile can't be removed

You can do this by providing an interface:

type flocker interface{
TryLock() error
Unlock() error
Path() string
}

type fakeFlock struct {
err bool
}

func (f fakeFlock) TryLock() error {
if f.err {
return errors.New("error")
}
return nil
}

func (f fakeFlock) Unlock() error {
if f.err {
return errors.New("error")
}
return nil
}

Remove blank line

count++

This flock line shouldn't. be here. So either a path change is needed or you need to run go tidy

Move these files under:

internal/accessor
accessor.go
file/
file.go
windows/
window.go

accessor.go:

• Defines type Cache interface{}
  file.go:
• Defines Accessor struct{}
• Defines New() constructor
  windows.go
• Defines Accessor struct{}
• Defines New() constructor

All "Accessor" types implement accessor.Cache