BUG report

[arthurkiller]

{"level":"error","ts":1561626561.314334,"caller":"continuous/continuous.go:239","msg":"wait child process to exit failed","pid":2362,"error":"waitid: invalid argument","stacktrace":"github.com/shafreeck/continuous.(*Cont).Serve\n\t/Users/arthur/golang/src/github.com/shafreeck/continuous/continuous.go:239\nmain.main\n\t/Users/arthur/golang/src/icode.baidu.com/baidu/bdrp/jarvis/bin/jarvis/main.go:138\nruntime.main\n\t/usr/local/go/src/runtime/proc.go:200"}
{"level":"error","ts":1561626561.3144157,"caller":"continuous/continuous.go:250","msg":"recover pid file failed","pid":2362,"error":"rename /home/work/agent/./jarvis.pid.old /home/work/agent/./jarvis.pid: no such file or directory","stacktrace":"github.com/shafreeck/continuous.(*Cont).Serve\n\t/Users/arthur/golang/src/github.com/shafreeck/continuous/continuous.go:250\nmain.main\n\t/Users/arthur/golang/src/icode.baidu.com/baidu/bdrp/jarvis/bin/jarvis/main.go:138\nruntime.main\n\t/usr/local/go/src/runtime/proc.go:200"}

use path.Join instead of appending the path