delete map[key] in go?

Question

I have a map:

var sessions =  map[string] chan int{}

How do I delete sessions[key]? I tried:

sessions[key] = nil,         


        

Answer 1

Copied from Go 1 release notes

In the old language, to delete the entry with key k from the map represented by m, one wrote the statement,

m[k] = value, false

This syntax was a peculiar special case, the only two-to-one assignment. It required passing a value (usually ignored) that is evaluated but discarded, plus a boolean that was nearly always the constant false. It did the job but was odd and a point of contention.

In Go 1, that syntax has gone; instead there is a new built-in function, delete. The call

delete(m, k)

will delete the map entry retrieved by the expression m[k]. There is no return value. Deleting a non-existent entry is a no-op.

Updating: Running go fix will convert expressions of the form m[k] = value, false into delete(m, k) when it is clear that the ignored value can be safely discarded from the program and false refers to the predefined boolean constant. The fix tool will flag other uses of the syntax for inspection by the programmer.