go-fastping randomly crash with panic: close of closed channel

[mateuszbbb]

Got random panic errors. Any way to fix this?

`time="2018-06-18T22:55:32+02:00" level=debug msg="Pinger iteration finished"
panic: close of closed channel

goroutine 10 [running]:
github.com/tatsushid/go-fastping.(*Pinger).run(0xc4202842d0, 0xc42010ce01)
/usr/local/src/go/src/github.com/tatsushid/go-fastping/fastping.go:479 +0x7c4
github.com/tatsushid/go-fastping.(*Pinger).Run(0xc4202842d0, 0x0, 0x0)
/usr/local/src/go/src/github.com/tatsushid/go-fastping/fastping.go:329 +0xee
main.ping_hosts_single(0xc4202c2dc0)
/usr/local/src/go/src/nlbhealthmonitor/main.go:261 +0xca
main.is_icmp_status_ok(0xc420210081)
/usr/local/src/go/src/nlbhealthmonitor/main.go:217 +0x37
`