I was still getting "io: read/write on closed pipe" errors in the logs,
even after comparing errors against io.ErrClosedPipe to skip logging
them. It turns out that kcp-go wraps many of its errors in another type.
The actual type of the errors was *errors.withStack, where errors is
https://github.com/pkg/errors. We can use the go1.13 errors interface
(https://blog.golang.org/go1.13-errors) to get at the value inside.
Recent versions of go (at least go1.14) automatically add a `go` line to
go.mod with every command, such as `go build`. Adding one here so that
builds don't wind up changing a versioned file. There doesn't seem to be
much importance to what number goes here
(https://utcc.utoronto.ca/~cks/space/blog/programming/GoModulesGoVersions).
I've just verified that the programs build with go1.11.
David Fifield