time.Now
GOROOT/src/time/time.go

  Total:       2.04s      2.22s (flat, cum)  1.01%
   1126            .          .           // we avoid ever reporting a monotonic time of 0. 
   1127            .          .           // (Callers may want to use 0 as "time not set".) 
   1128            .          .           var startNano int64 = runtimeNano() - 1 
   1129            .          .            
   1130            .          .           // Now returns the current local time. 
   1131        120ms      300ms           func Now() Time { 
   1132        1.85s      1.85s           	sec, nsec, mono := now() 
   1133         30ms       30ms           	mono -= startNano 
   1134         10ms       10ms           	sec += unixToInternal - minWall 
   1135         10ms       10ms           	if uint64(sec)>>33 != 0 { 
   1136            .          .           		// Seconds field overflowed the 33 bits available when 
   1137            .          .           		// storing a monotonic time. This will be true after 
   1138            .          .           		// March 16, 2157. 
   1139            .          .           		return Time{uint64(nsec), sec + minWall, Local} 
   1140            .          .           	} 
   1141         20ms       20ms           	return Time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, Local} 
   1142            .          .           } 
   1143            .          .            
   1144            .          .           func unixTime(sec int64, nsec int32) Time { 
   1145            .          .           	return Time{uint64(nsec), sec + unixToInternal, Local} 
   1146            .          .           }