Install the package in your environment:
go get github.com/dpapathanasiou/go-recaptcha
To use it within your own code, import "github.com/dpapathanasiou/go-recaptcha" and call:
once, to set the reCaptcha private key for your domain, then:
recaptcha.Confirm (clientIpAddress, recaptchaResponse)
for each reCaptcha form input you need to check, using the values obtained by reading the form's POST parameters (the "recaptchaResponse" in the above corresponds to the value of "g-recaptcha-response" sent by the reCaptcha server.)
The recaptcha.Confirm() function returns either true (i.e., the captcha was completed correctly) or false.
Included with this repo is example.go, a simple HTTP server which creates the reCaptcha form and tests the input.
See the instructions for running the example for more details.