Example Scenario
I have an AWS S3 bucket with lots of object which a couple of my application needs to access. The applications use some info available to them to form the S3 object name, get the object and run a transformation on the object data before using it for further processing specific to the application.
I would like to create a module which will hold the logic for forming the object name, obtain it from S3 and then run the transformation on the object data so that I wont be duplicating these functions in multiple places.
In this scenario should I add AWS SDK as a dependency in the module? Keep in mind that the applications might have to use AWS SDK for something else specific to that application or they might not require it at all.
In general what is the best way to solve problems like this i.e where to add the dependency? And how to manage different versions?
If your code has to access packages from the AWS SDK then yes, you have no choice but to add it as dependency. If it doesn't and the logic is generic, or you can abstract it away from the AWS SDK then you don't need the dependency (and in fact the go tooling like go mod tidy will remove the dependency from go.mod if you add it)
In this scenario should I add AWS SDK as a dependency in the module? Keep in mind that the applications might have to use AWS SDK for something else specific to that application or they might not require it at all.
Yes, if any package from your module depends on AWS SDK, Go Modules system is going to add AWS SDK as a dependency for your module. There is nothing special you are supposed to do with your module.
Try this script with Go 1.11 or higher (and make sure to work out of GOPATH):
Tree:
moduledir/packagedir1
moduledir/packagedir2
Recipe:
cd moduledir
go mod init moduledir ;# or go mod init github.com/user/moduledir
Recipe:
go install ./packagedir1
go install ./packagedir2
Module things are supposed to automagically work!
In general what is the best way to solve problems like this i.e where to add the dependency? And how to manage different versions?
The Modules system is going to automatically manage dependencies for your module and record them in the files go.mod and go.sum. If you need to override some dependency, you should use the 'go get' command for that. For instance, see this question: How to point Go module dependency in go.mod to a latest commit in a repo?
You can also find much information on Modules here: https://github.com/golang/go/wiki/Modules