Add new rule: function call in async assertions

[nunnatsa]

Description

The linter now warns about using Eventually or Consistently with a function call. This is because when doing that, Eventually checks the same returned value again and again, instead of polling by calling the function.

For example:

func slowInt() int {
    time.Sleep(time.Second)
    return 42
}

...

It("should test that slowInt returns 42, eventually", func() {
    Eventually(slowInt()).WithPolling(time.Millisecond * 100).WithTimeout(time.Second * 2).Equal(42)
})

In the above code, Eventually receives 42 as its argument. Then it polls this value to check if it equal

42. What we really wanted here is:

It("should test that slowInt returns 42, eventually", func() {
    Eventually(slowInt).WithPolling(time.Millisecond * 100).WithTimeout(time.Second * 2).Equal(42)
})

Now, Eventually calls the function until it returns the required value.

To suppress this warning entirely, add the --suppress-async-assertion=true command line flag, or the ginkgo-linter:ignore-async-assert-warning comment.

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)
• [x] This change requires a documentation update

How Has This Been Tested?

• [x] Added test case and related test data
• [x] Update the functional test

Checklist:

• [x] I have performed a self-review of my own code
• [X] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [X] New and existing unit tests pass locally with my changes
• [X] Any dependent changes have been merged and published in downstream modules
• [x] I ran golangci-lint

[coveralls]

Pull Request Test Coverage Report for Build 4469374789

• 69 of 72 (95.83%) changed or added relevant lines in 2 files are covered.
• 5 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.8%) to 83.964%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
types/config.go	2	3	66.67%
ginkgo_linter.go	67	69	97.1%
<!--	Total:	69	72	95.83%	-->

Files with Coverage Reduction	New Missed Lines	%
types/config.go	1	33.33%
ginkgo_linter.go	4	89.34%
<!--	Total:	5		-->

Totals
Change from base Build 4468477451:	0.8%
Covered Lines:	754
Relevant Lines:	898

---

💛 - Coveralls