Question

How do I check whether a channel has a value for me to read?

I don’t want to block when reading a channel. I want to see whether it has a value. If it does have one, I’ll read it. If it doesn’t have one (yet), I’ll do something else and check back again later.

Answer 1

WARNING: This is no longer accurate, see the answer below.

From the docs:

If a receive expression is used in an
assignment or initialization of the
form

x, ok = <-ch
x, ok := <-ch
var x, ok = <-ch

the receive operation becomes
non-blocking. If the operation can
proceed, the boolean variable ok will
be set to true and the value stored in
x; otherwise ok is set to false and x
is set to the zero value for its type