Update readme for performance bits

Readme.md

@@ -114,9 +114,9 @@ Performance
 
 A key feature of Dapper is performance. The following metrics show how long it takes to execute a `SELECT` statement against a DB (in various config, each labeled) and map the data returned to objects.
 
-The benchmarks can be found in [Dapper.Tests.Performance](https://github.com/StackExchange/Dapper/tree/master/Dapper.Tests.Performance) (contributions welcome!) and can be run once compiled via:
-```
-Dapper.Tests.Performance.exe -f * --join
+The benchmarks can be found in [Dapper.Tests.Performance](https://github.com/StackExchange/Dapper/tree/master/Dapper.Tests.Performance) (contributions welcome!) and can be run via:
+```bash
+dotnet run -p .\Dapper.Tests.Performance\ -c Release -f netcoreapp3.0 -- -f * --join
 ```
 Output from the latest run is:
 ``` ini