Use WaitGroup to block extension loop iteration until apm server request is complete

[estolfo]

Use the WaitGroup to block the extension for loop iteration from completing until the go routine sending to the apm server has returned.

Resolves #128

[ghost]

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• Start Time: 2022-03-02T10:42:18.827+0000

• Duration: 6 min 26 sec

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Test	Results
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Passed	84
Skipped	6
Total	90

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[jlvoiseux]

Looks great to me, it should solve #128