Hmac-SHA256 for aws

[hectorvp]

Can anyone tell me how can i use this code for aws signature generation.
It is step 3 of aws signature generation.
Link of aws doc : https://docs.aws.amazon.com/general/latest/gr/sigv4-calculate-signature.html

Signature generated does not match .......sample input is given in aws document.

[Rafael Lüder]

@hectorvp this is an old one but my comment on #39 should help.