Describe the bug

A clear and concise description of what the bug is.
amw := authenticationMiddleware{}
when use Populate panic
below is right
amw := authenticationMiddleware{tokenUsers: make(map[string]string)}
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Versions

Go version: go version
package version: run git rev-parse HEAD inside the repo

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Steps to Reproduce

How can the bug be triggered?

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Expected behavior

What output or behaviour were you expecting instead?

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Code Snippets

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