Function arguments do not color functions. If you'd like to call a function that takes a Context argument without it, just pass in a context.Background(). It's a non-issue.
Full rebuttal by jerf here: https://news.ycombinator.com/item?id=39317648
Coloring is a non-issue, context itself is. Newcomers find it unintuitive, and implementing a cancellable piece of work is incredibly cumbersome. One can only cancel a read/write to a channel, implementing cancellation implies a 3 line increase to every channel operation, cancelling blocking I/O defers to the catchphrase that utilises the name of the language itself.
Cancelling blocking IO is such a pain point in Go indeed. One can do it via careful Close() calls from another goroutine while ensuring that close is called only once. But Go provides absolutely no help for that in the standard library.
I had a need for that, on TCP and UDP connections. The former behind a net.Conn.
Rather than fiddle with Close() calls, from memory what I found worked was setting a short (or in the past) deadline on the Conn (SetReadDeadline). This as it is documented as applying even to an existing blocked call, and makes that blocked call eventually return an error.
So when I wanted to tear down the TCP connection and clean up the various goroutines associated with using the connection, I'd unblock any blocking i/o, then eventually one had an easy Close() call on the connection.
UDP was simpler, as each i/o operation had a short timeout. I've not investigated what could be done for pipe and fifo i/o.
By the same token, being async doesn't color a function since you can always blocking-wait on the returned promise. But then the callers of that function can't use it async.
Similarly with Context, if your function calls other functions with Context but always passes in Background(), you deprive your callers of the ability to provide their own Context, which is kinda important. So in practice you still end up adding that argument throughout the entire call hierarchy all the way up to the point where the context is no longer relevant.