Not an agency per se, but you should probably check out Weekday (https://weekday.works). They have a good database of folks that you can reach out to using their own platform (or they can do it for you). And they're cheap. 5 or 7% I think. Source: about 1 year ago

One way could be to Go related Job Boards, where Go Developers are checking for they language/skills related Jobs. For Go there are golangjob.xyz , golangproject.com and golang.cafe For golangjob.xyz you can get a 20% discount on a Job Ad with the coupon REDIT202022. Source: almost 2 years ago

Would be great to know where you post your golang jobs. I use normally https://golangjob.xyz or https://golang.cafe. Source: almost 2 years ago

I invite you to be one of my >14k followers. I (not a bot) tweet about Go related OS projects/libraries/news and from time to time Golang Jobs from my Golang Jobs Board: Https://twitter.com/golangch. Source: about 2 years ago

Another 53y dev, started with Basic, VB.NET,C#,Java,Java/Typescript and for backend since 7 years Golang. In my day job I am CPO, but code at least every weekend in Go, for example, my Golang Jobs Board or Tweeting about Go-related stuff on https://twitter.com/golangch. Source: about 2 years ago

There are Go-specific Job Boards to post open positions like eg https://golangjob.xyz ( Use REDDIT0210 as a coupon code to get a 10% discount ). Source: over 2 years ago