Add additional golang linters

[maggie44]

Detect issues like unhandled errors: #365

[nhooyr]

Hey @maggie44 I appreciate the PR but I'm not a fan of a lot of the automated linters beyond go vet and golint. I find they force you to write code that isn't any more correct just to satisfy the linter and so the code ends up being less clear and more verbose. So I'd prefer to not add anything beyond what I already have.

[nhooyr]

And the cited issue would not have been detected by a linter because I was explicitly ignoring the error with _.

[maggie44]

No problem, was worth a look.

Here is the output of the linter on the current master branch, probably worth a look, although I know master is a bit behind dev now so not sure how many are still relevant:

autobahn_test.go:132:22: Error return value of `wstest.Process.Kill` is not checked (errcheck)
                wstest.Process.Kill()
                                   ^
conn_test.go:162:17: Error return value of `n1.SetDeadline` is not checked (errcheck)
                n1.SetDeadline(d)
                              ^
conn_test.go:163:17: Error return value of `n1.SetDeadline` is not checked (errcheck)
                n1.SetDeadline(time.Time{})
                              ^
autobahn_test.go:95:25: SA4009: argument ctx is overwritten before first use (staticcheck)
func wstestClientServer(ctx context.Context) (url string, closeFn func(), err error) {
                        ^
autobahn_test.go:113:2: SA4009(related information): assignment to ctx (staticcheck)
        ctx, cancel := context.WithTimeout(context.Background(), time.Minute*15)
        ^
compress_notjs.go:103:27: Error return value of `(github.com/klauspost/compress/flate.Resetter).Reset` is not checked (errcheck)
        fr.(flate.Resetter).Reset(r, dict)
                                 ^
netconn.go:145:20: Error return value of `c.SetWriteDeadline` is not checked (errcheck)
        c.SetWriteDeadline(t)
                          ^
netconn.go:146:19: Error return value of `c.SetReadDeadline` is not checked (errcheck)
        c.SetReadDeadline(t)
                         ^
read.go:60:11: Error return value of `c.Reader` is not checked (errcheck)
                c.Reader(ctx)
                        ^
write.go:385:14: Error return value of `bw.WriteByte` is not checked (errcheck)
        bw.WriteByte(0)
                    ^
accept.go:278:6: func `acceptWebkitDeflate` is unused (unused)
func acceptWebkitDeflate(w http.ResponseWriter, ext websocketExtension, mode CompressionMode) (*compressionOptions, error) {
     ^
netconn.go:154:22: S1024: should use time.Until instead of t.Sub(time.Now()) (gosimple)
                c.writeTimer.Reset(t.Sub(time.Now()))
                                   ^
netconn.go:163:21: S1024: should use time.Until instead of t.Sub(time.Now()) (gosimple)
                c.readTimer.Reset(t.Sub(time.Now()))
                                  ^
compress_notjs.go:159:26: SA6002: argument should be pointer-like to avoid allocations (staticcheck)
        swPool[cap(sw.buf)].Put(sw.buf)
                                ^
accept.go:83:9: SA4001: &*x will be simplified to x. It will not copy x. (staticcheck)
        opts = &*opts
               ^
dial.go:73:9: SA4001: &*x will be simplified to x. It will not copy x. (staticcheck)
        opts = &*opts
               ^
dial.go:246:10: SA4001: &*x will be simplified to x. It will not copy x. (staticcheck)
        copts = &*copts
                ^
frame_test.go:57:11: SA4030: (*math/rand.Rand).Intn(n) generates a random value 0 <= x < n; that is, the generated values don't include n; r.Intn(1) therefore always returns 0 (staticcheck)
                        return r.Intn(1) == 0
``

[nhooyr]

Some good ones in there, I'll get them in #256. Definitely not against running them occasionally to filter the false positives. Thanks @maggie44

[nhooyr]

Ended up adding staticcheck at least in #256. Thanks again @maggie44