panic: runtime error: index out of range [0] with length 0

[y0tsawin]

panic: runtime error: index out of range [0] with length 0

goroutine 141 [running]:
main.getMetric(0xc0000100f8, 0xc0001371e0, 0xe, 0xaf2c88, 0x0)
/root/googleanalytics_exporter/ganalytics.go:111 +0x2a9
main.main.func2(0xc0000100f8, 0xc0001371e0, 0xe)
/root/googleanalytics_exporter/ganalytics.go:93 +0x43
created by main.main
/root/googleanalytics_exporter/ganalytics.go:92 +0x4a5

I do not know if this problem has ever been encountered or not. And how can I fix it ?
This problem occurs when I run ./ganalytics