`cfssl genkey` fails to return probably 3/10 times

I'm seeing the following:

```
$ cfssl genkey prometheus.csr.json`

2018/01/19 13:25:52 [INFO] generate received request
2018/01/19 13:25:52 [INFO] received CSR
2018/01/19 13:25:52 [INFO] generating key: rsa-4096
```
3/10 times it just hangs there and never advances.

here is the csr.json

```
{
"CN": "prometheus2.platform.r53.nordstrom.net",
"hosts": [
"127.0.0.1",
"*.xxxx.svc.cluster.local",
"yyyy",
"zzzz",
"aaaaa",
"bbbb"
],
"key": {
"algo": "rsa",
"size": 4096
},
"names": [
{
"C": "US",
"L": "Seattle",
"O": "Nordstrom",
"OU": "noneya@nordstrom.com",
"ST": "Washington"
}
]
}
```

```
$ cfssl version
Version: 1.2.0
Revision: dev
Runtime: go1.6.2
```