func checkGoSum()

in gosumcheck/main.go [96:146]
47 lines of code
11 McCabe index (conditional complexity)

func checkGoSum(client *sumdb.Client, name string, data []byte) {
	lines := strings.Split(string(data), "\n")
	if lines[len(lines)-1] != "" {
		log.Printf("error: final line missing newline")
		return
	}
	lines = lines[:len(lines)-1]

	errs := make([]string, len(lines))
	var wg sync.WaitGroup
	for i, line := range lines {
		wg.Add(1)
		go func(i int, line string) {
			defer wg.Done()
			f := strings.Fields(line)
			if len(f) != 3 {
				errs[i] = "invalid number of fields"
				return
			}

			dbLines, err := client.Lookup(f[0], f[1])
			if err != nil {
				if err == sumdb.ErrGONOSUMDB {
					errs[i] = fmt.Sprintf("%s@%s: %v", f[0], f[1], err)
				} else {
					// Otherwise Lookup properly adds the prefix itself.
					errs[i] = err.Error()
				}
				return
			}
			hashAlgPrefix := f[0] + " " + f[1] + " " + f[2][:strings.Index(f[2], ":")+1]
			for _, dbLine := range dbLines {
				if dbLine == line {
					return
				}
				if strings.HasPrefix(dbLine, hashAlgPrefix) {
					errs[i] = fmt.Sprintf("%s@%s hash mismatch: have %s, want %s", f[0], f[1], line, dbLine)
					return
				}
			}
			errs[i] = fmt.Sprintf("%s@%s hash algorithm mismatch: have %s, want one of:\n\t%s", f[0], f[1], line, strings.Join(dbLines, "\n\t"))
		}(i, line)
	}
	wg.Wait()

	for i, err := range errs {
		if err != "" {
			fmt.Printf("%s:%d: %s\n", name, i+1, err)
		}
	}
}