Replace use of strings.Title with cases.Title

[tmc]

This removes the use of the deprecated strings.Title function and enables go 1.18 in CI while still working on Go 1.16+.

Depends on #2266 (will rebase once that's in).

[coveralls]

Coverage increased (+0.06%) to 75.075% when pulling 4f3aaac on tmc:use-cases into 0c11e5f on 99designs:master.

[a8m]

Looks good to me. My only concern before merging is if we introduce any breaking change by moving from strings.Title to cases.Title. Can you check please and add a link here? Thanks

[StevenACoffman]

Thanks! This was reported to Go in 2013 in golang/go#6801.

I think that your usage of cases.Title(language.English, cases.NoLower) is pretty safe as NoLower avoids trampling on initialisms like those listed here. I think otherwise language.English matches the current behavior for now, and it opens the possibility of supporting multilingual in the future through some configuration without speculatively adding that complexity now. We can see if there's much demand for that in the future.

Given that, I'm not sure if adding further unit tests are necessary now, but as a note to our future selves, the two test cases I have used elsewhere for multilingual capitalization are dealing with unicode punctuation and language specific capitalization.

1. Unicode punctuation can be tested like this:

import (
    "fmt"
    "strings"
)

func main() {
    a := strings.Title("go.go\u2024go")
    b := "Go.Go\u2024Go"
    if a != b {
        fmt.Printf("%s != %s\n", a, b) // Go.Go․go != Go.Go․Go
    }
}

2. The language specific test case I've used is in Dutch words, "ijsland" should be capitalized as "IJsland", but the strings.Title("ijsland") is converted to "Ijsland".

caser := cases.Title(language.Dutch)
caser.String("ijsland") // Ijsland

[StevenACoffman]

golang.org/x/text/cases currently has a go.mod with a go directive that indicates that the module was written assuming the semantics of the Go version 1.17 as here https://cs.opensource.google/go/x/text/+/master:go.mod;l=10 but appears to work fine in Go 1.16 as all gqlgen tests still pass in Go 1.16.