unknown directive: toolchain

**Describe the bug**
try to call `go install` and got:
```
go: errors parsing go.mod:
/lazydocker-git/go.mod:5: unknown directive: toolchain
```
go version go1.13.8 linux/amd64

**To Reproduce**
checkout

**Expected behaviour**
installed binary

**Desktop (please complete the following information):**
- The last commit id if you built project from sources (run : ```git rev-parse HEAD```)
7e7aadc2071d58031bf2daafca1fbd4093efc23f

**Additional context**
Add any other context about the problem here.

Start by reading go.mod, especially the directive on line 5, and compare it with the reported Go 1.13.8 environment. Check how the project's declared Go requirements relate to go install. Done means the supported installation path is clear and the reported parsing failure is resolved or explicitly documented.

Written by the indexing model from the issue text.