Respond to code review feedback

change logic in version.go so that the trial related messages only appear on trial versions of molecula
convert Command methods in trial.go to functions and  pass a loggerLogger variable instead since that was the only piece of Command being used
add a function named expireAfter which seperately runs similar functionality to what was previously in daily check with chnages directed at stopping users from changing their internal clock date
change variable names and placement to be more readable and organized

server/server.go

@@ -285,7 +285,7 @@ func (m *Command) SetupServer() error {
 
 	m.logger.Printf("%s", pilosa.VersionInfo())
 
-	m.trialVersion()
+	trialVersion(m.logger)
 
 	// If the pilosa command line uses -tx to override the
 	// PILOSA_TXSRC env variable, then we must also correct

server/trial.go

@@ -1,4 +1,4 @@
-// Copyright 2017 Pilosa Corp.
+// Copyright 2021 Pilosa Corp.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -27,54 +27,56 @@ import (
 	"github.com/pilosa/pilosa/v2"
 )
 
-func (m *Command) trialVersion() {
+func trialVersion(logger loggerLogger) {
 	if pilosa.TrialDeadline != "" {
-		endTime, err := time.Parse("2006-01-02", pilosa.TrialDeadline)
+		startTime, err := ntpServerTime(4, logger)
 		if err != nil {
-			m.logger.Printf("parsing trial deadline: %v", err)
+			logger.Printf("reading ntp server time %v", err)
 			os.Exit(1)
 		}
-		go m.dailyCheck(endTime)
+		endTime, err := time.Parse("2006-01-02", pilosa.TrialDeadline)
+		if err != nil {
+			logger.Printf("parsing trial deadline: %v", err)
+			os.Exit(1)
+		}
+		maxDuration := endTime.Sub(startTime)
+		go expireAfter(maxDuration, logger)
+		go dailyCheck(maxDuration, logger)
 	}
 }
 
 const trialCheckInterval = 24 * time.Hour
 
 // dailyCheck runs in the background while a trial version of Molecula is being run, displaying daily reminders of the remaining days
-func (m *Command) dailyCheck(endTime time.Time) {
+func dailyCheck(maxDuration time.Duration, logger loggerLogger) {
+	startTime := time.Now() // we get a new start time here to ensure that it has a monotonic clock
+	remaining := maxDuration - time.Since(startTime)
+	logger.Printf("Current time remaining in trial: %d days %v", remaining/(time.Hour*24), remaining%(time.Hour*24))
 	ticker := time.NewTicker(trialCheckInterval)
-	startTime, err := m.ntpServerTime(4)
-	if err != nil {
-		m.logger.Printf("reading ntp server time %v", err)
-		os.Exit(1)
-	}
-	runDuration := endTime.Sub(startTime)
-	if runDuration <= 0 {
-		m.logger.Printf("Trial edition of Molecula has expired, exiting now!")
-		os.Exit(1)
-	}
 	for range ticker.C {
-		runningDuration := time.Since(startTime)
-		m.logger.Printf("Current time remaining in trial: %v", runDuration-runningDuration)
-		if runningDuration >= runDuration {
-			m.logger.Printf("Trial edition of Molecula has expired, exiting now!")
-			os.Exit(1)
-		}
+		remaining := maxDuration - time.Since(startTime)
+		logger.Printf("Current time remaining in trial: %d days %v", remaining/(time.Hour*24), remaining%(time.Hour*24))
 	}
 }
 
-const ntpurl = "0.beevik-ntp.pool.ntp.org"
+const ntpURL = "0.beevik-ntp.pool.ntp.org"
 const ntpRetryDelay = 100 * time.Millisecond
 
 // ntpServerTime attempts to reach ntp servers with delays between each attempt, returning the time value of the first connected server
-func (m *Command) ntpServerTime(retries int) (time.Time, error) {
-	t, err := ntp.Time(ntpurl)
+func ntpServerTime(retries int, logger loggerLogger) (time.Time, error) {
+	t, err := ntp.Time(ntpURL)
 	if err != nil && retries <= 0 {
 		return t, err
 	}
 	if err != nil {
 		time.Sleep(ntpRetryDelay)
-		return m.ntpServerTime(retries - 1)
+		return ntpServerTime(retries-1, logger)
 	}
 	return t, nil
 }
+
+func expireAfter(maxDuration time.Duration, logger loggerLogger) {
+	time.Sleep(maxDuration)
+	logger.Printf("Trial edition of Molecula has expired, exiting now!")
+	os.Exit(1)
+}

version.go

@@ -53,8 +53,10 @@ func VersionInfo() string {
 	case buildTime != "":
 		suffix += " (" + buildTime + ")"
 	}
-	suffix += " " + GoVersion + " limited time trial ends at: " + TrialDeadline
-
+	suffix += " " + GoVersion
+	if TrialDeadline != "" {
+		suffix += " limited time trial ends at: " + TrialDeadline
+	}
 	return prefix + "Pilosa" + suffix
 }