golang sync.Map Range函数线程安全吗？

Question

From the doc

Range does not necessarily correspond to any consistent snapshot of the 
Map's contents: no key will be visited more than once, but if the value 
for any key is stored or deleted concurrently, Range may reflect any 
mapping for that key from any point during the Range call.

Does this mean that no read lock is invoked during range call and user must implements his own mutex in order for Range call to be thread safe?

Answer 1

You hit it pretty spot on.

Basically, this works the same way you'd use for: You're just grabbing a count up front, and then iterating each value you expect to exist.

Ideally, if you have to worry about concurrency on the map, you should make a copy that you then iterate, or implement a sync.Mutex around it.