Map with concurrent access

When you use a map in a program with concurrent access, is there any need to use a mutex in functions to read values?

Solution 1:

Multiple readers, no writers is okay:

https://groups.google.com/d/msg/golang-nuts/HpLWnGTp-n8/hyUYmnWJqiQJ

One writer, no readers is okay. (Maps wouldn't be much good otherwise.)

Otherwise, if there is at least one writer and at least one more either writer or reader, then all readers and writers must use synchronization to access the map. A mutex works fine for this.

Solution 2:

sync.Map has merged to Go master as of April 27, 2017.

This is the concurrent Map we have all been waiting for.

https://github.com/golang/go/blob/master/src/sync/map.go

https://godoc.org/sync#Map

Solution 3:

I answered your question in this reddit thread few days ago:

In Go, maps are not thread-safe. Also, data requires locking even for reading if, for example, there could be another goroutine that is writing the same data (concurrently, that is).

Judging by your clarification in the comments, that there are going to be setter functions too, the answer to your question is yes, you will have to protect your reads with a mutex; you can use a RWMutex. For an example you can look at the source of the implementation of a table data structure (uses a map behind the scenes) which I wrote (actually the one linked in the reddit thread).