Don't format the error message unless it is really needed

[fd]

No description provided.

[coveralls]

Coverage increased (+0.009%) to 82.234% when pulling b16d2fd on mrhenry:lazy-invariant into 9b5a661 on graphql-go:master.

[fd]

benchmark                       old ns/op       new ns/op      delta
BenchmarkListQuery_1-4          349864          243236         -30.48%
BenchmarkListQuery_100-4        3534198         1586335        -55.11%
BenchmarkListQuery_1K-4         32966933        13725420       -58.37%
BenchmarkListQuery_10K-4        308862819       140592678      -54.48%
BenchmarkListQuery_100K-4       2255458560      981282854      -56.49%
BenchmarkWideQuery_1_1-4        159626          140584         -11.93%
BenchmarkWideQuery_10_1-4       960218          582556         -39.33%
BenchmarkWideQuery_100_1-4      62290987        30767558       -50.61%
BenchmarkWideQuery_1K_1-4       6342374529      2840497529     -55.21%
BenchmarkWideQuery_1_10-4       196672          170694         -13.21%
BenchmarkWideQuery_10_10-4      2356517         1197957        -49.16%
BenchmarkWideQuery_100_10-4     190874887       78918530       -58.65%
BenchmarkWideQuery_1K_10-4      20784765533     8915631619     -57.10%

[coveralls]

Coverage decreased (-0.02%) to 82.23% when pulling d951837 on mrhenry:lazy-invariant into 77b1ae5 on graphql-go:master.

[chris-ramon]

pretty awesome!, thanks @fd 🚢