Minor refactors across the codebase to improve readability and use more efficient APIs: replace fmt.Sprintf+base64 encoding with fmt.Appendf when building Shadowsocks userInfo; compute elapsed using max(now-prev.at, window) to simplify logic; use strings.SplitSeq for splitting in two places; simplify test and goroutine loops to range-based iterations and use errgroup's Go helper; and align/clean up struct field formatting and test map literals. Mostly stylistic/efficiency changes with no intended behavior changes.
The process cmd, done and exitErr fields were written by Start/startCommand and
the waitForCommand goroutine while IsRunning/GetErr/GetResult/Stop read them
concurrently from other goroutines (the status endpoint and the check-xray
job) — a data race. Guard them with a RWMutex: writers take the write lock;
readers snapshot under the read lock and run any blocking syscall
(Wait/Signal/Kill) on the local copy without holding it. IsRunning now uses the
done channel as the exit signal instead of reading cmd.ProcessState, which
races with cmd.Wait. Adds a -race regression test.
MHSanaei