It's possible the JSON serialization in rust may sway results unfavourably towards go.
Rust:
siege -c 50 -t1 http://localhost:1337
Lifting the server siege...
Transactions: 32824 hits
Availability: 99.86 %
Elapsed time: 60.96 secs
Data transferred: 0.56 MB
Response time: 0.02 secs
Transaction rate: 538.45 trans/sec
Throughput: 0.01 MB/sec
Concurrency: 12.71
Successful transactions: 32824
Failed transactions: 45
Longest transaction: 19.51
Shortest transaction: 0.00
siege -c 50 -t5 http://localhost:1337
Lifting the server siege...
Transactions: 163929 hits
Availability: 99.82 %
Elapsed time: 300.18 secs
Data transferred: 2.81 MB
Response time: 0.04 secs
Transaction rate: 546.10 trans/sec
Throughput: 0.01 MB/sec
Concurrency: 24.53
Successful transactions: 163929
Failed transactions: 293
Longest transaction: 20.66
Shortest transaction: 0.00
siege -c 10 -t1 http://localhost:1337
Lifting the server siege...
Transactions: 32744 hits
Availability: 99.97 %
Elapsed time: 60.82 secs
Data transferred: 0.56 MB
Response time: 0.00 secs
Transaction rate: 538.38 trans/sec
Throughput: 0.01 MB/sec
Concurrency: 2.57
Successful transactions: 32744
Failed transactions: 9
Longest transaction: 19.51
Shortest transaction: 0.00
Go
siege -c 50 -t1 http://localhost:1338
Lifting the server siege...
Transactions: 32848 hits
Availability: 99.87 %
Elapsed time: 60.30 secs
Data transferred: 0.56 MB
Response time: 0.03 secs
Transaction rate: 544.74 trans/sec
Throughput: 0.01 MB/sec
Concurrency: 17.28
Successful transactions: 32848
Failed transactions: 43
Longest transaction: 19.51
Shortest transaction: 0.00
siege -c 50 -t5 http://localhost:1338
Lifting the server siege...
Transactions: 163975 hits
Availability: 99.89 %
Elapsed time: 300.46 secs
Data transferred: 2.81 MB
Response time: 0.06 secs
Transaction rate: 545.75 trans/sec
Throughput: 0.01 MB/sec
Concurrency: 34.22
Successful transactions: 163975
Failed transactions: 175
Longest transaction: 21.18
Shortest transaction: 0.00
siege -c 10 -t1 http://localhost:1338
Lifting the server siege...
Transactions: 32754 hits
Availability: 99.98 %
Elapsed time: 60.05 secs
Data transferred: 0.56 MB
Response time: 0.01 secs
Transaction rate: 545.45 trans/sec
Throughput: 0.01 MB/sec
Concurrency: 4.69
Successful transactions: 32754
Failed transactions: 7
Longest transaction: 19.52
Shortest transaction: 0.00