Remove extra colon in Direct Authentication example

[rehandaphedar]

Since the variable names are already included in the function declaration, golang will throw an error:

no new variables on left side of :=

[coveralls]

Pull Request Test Coverage Report for Build 11068850611

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 83.285%

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Totals
Change from base Build 10983597847:	0.0%
Covered Lines:	2591
Relevant Lines:	3111

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💛 - Coveralls