bombardier 
bombardier is a HTTP(S) benchmarking tool. It is written in Go programming language and uses excellent fasthttp instead of Go's default http library, because of its lightning fast performance.
With bombardier v1.1 and higher you can now use net/http client if you need to test HTTP/2.x services or want to use a more RFC-compliant HTTP client.
Tested on go1.8 and higher.
Installation
You can grab binaries in the releases section. Alternatively, to get latest and greatest run:
go get -u github.com/codesenberg/bombardier
Usage
bombardier [<flags>] <url>
For a more detailed information about flags consult GoDoc.
Known issues
AFAIK, it's impossible to pass Host header correctly with fasthttp, you can use net/http(--http1/--http2 flags) to workaround this issue.
Examples
Example of running bombardier against this server:
> bombardier -c 125 -n 10000000 http://localhost:8080
Bombarding http://localhost:8080 with 10000000 requests using 125 connections
10000000 / 10000000 [============================================] 100.00% 37s Done!
Statistics Avg Stdev Max
Reqs/sec 264560.00 10733.06 268434
Latency 471.00us 522.34us 51.00ms
HTTP codes:
1xx - 0, 2xx - 10000000, 3xx - 0, 4xx - 0, 5xx - 0
others - 0
Throughput: 292.92MB/s
Or, against a realworld server(with latency distribution):
> bombardier -c 200 -d 10s -l http://ya.ru
Bombarding http://ya.ru for 10s using 200 connections
[=========================================================================] 10s Done!
Statistics Avg Stdev Max
Reqs/sec 6607.00 524.56 7109
Latency 29.86ms 5.36ms 305.02ms
Latency Distribution
50% 28.00ms
75% 32.00ms
90% 34.00ms
99% 48.00ms
HTTP codes:
1xx - 0, 2xx - 0, 3xx - 66561, 4xx - 0, 5xx - 0
others - 5
Errors:
dialing to the given TCP address timed out - 5
Throughput: 3.06MB/s