Bump golangci-lint and (max) Go versions (#219)

Lint is failing with some inscrutable panic (on a commit with no code
changes). Let's try bumping the version in case they fixed it.

Additionally, the new version's github action uses Go 1.19, which means
it pulls in gofmt updates to match the new [doc-comment formatting rules][1].
So I added Go 1.19 to our list of versions to test (fixes #216)
and updated some of our doc-comments to format better in the
new world (mostly using the new link syntax).

[1]: https://go.dev/doc/comment

Test plan: make lint

graphql/client.go

@@ -46,31 +46,39 @@ type client struct {
 	method     string
 }
 
-// NewClient returns a Client which makes requests to the given endpoint,
+// NewClient returns a [Client] which makes requests to the given endpoint,
 // suitable for most users.
 //
 // The client makes POST requests to the given GraphQL endpoint using standard
-// GraphQL HTTP-over-JSON transport.  It will use the given http client, or
-// http.DefaultClient if a nil client is passed.
+// GraphQL HTTP-over-JSON transport.  It will use the given [http.Client], or
+// [http.DefaultClient] if a nil client is passed.
 //
 // The typical method of adding authentication headers is to wrap the client's
-// Transport to add those headers.  See example/caller.go for an example.
+// [http.Transport] to add those headers.  See [example/main.go] for an
+// example.
+//
+// [example/main.go]: https://github.com/Khan/genqlient/blob/main/example/main.go#L12-L20
 func NewClient(endpoint string, httpClient Doer) Client {
 	return newClient(endpoint, httpClient, http.MethodPost)
 }
 
-// NewClientUsingGet returns a Client which makes requests to the given endpoint,
-// suitable for most users.
+// NewClientUsingGet returns a [Client] which makes GET requests to the given
+// endpoint suitable for most users who wish to make GET requests instead of
+// POST.
 //
-// The client makes GET requests to the given GraphQL endpoint using a GET query,
-// with the query, operation name and variables encoded as URL parameters.
-// It will use the given http client, or http.DefaultClient if a nil client is passed.
+// The client makes GET requests to the given GraphQL endpoint using a GET
+// query, with the query, operation name and variables encoded as URL
+// parameters.  It will use the given [http.Client], or [http.DefaultClient] if
+// a nil client is passed.
 //
-// The client does not support mutations, and will return an error if passed a request
-// that attempts one.
+// The client does not support mutations, and will return an error if passed a
+// request that attempts one.
 //
 // The typical method of adding authentication headers is to wrap the client's
-// Transport to add those headers.  See example/caller.go for an example.
+// [http.Transport] to add those headers.  See [example/main.go] for an
+// example.
+//
+// [example/main.go]: https://github.com/Khan/genqlient/blob/main/example/main.go#L12-L20
 func NewClientUsingGet(endpoint string, httpClient Doer) Client {
 	return newClient(endpoint, httpClient, http.MethodGet)
 }
@@ -82,18 +90,20 @@ func newClient(endpoint string, httpClient Doer, method string) Client {
 	return &client{httpClient, endpoint, method}
 }
 
-// Doer encapsulates the methods from *http.Client needed by Client.
-// The methods should have behavior to match that of *http.Client
+// Doer encapsulates the methods from [*http.Client] needed by [Client].
+// The methods should have behavior to match that of [*http.Client]
 // (or mocks for the same).
 type Doer interface {
 	Do(*http.Request) (*http.Response, error)
 }
 
 // Request contains all the values required to build queries executed by
-// the graphql.Client.
+// the [Client].
 //
 // Typically, GraphQL APIs will accept a JSON payload of the form
+//
 //	{"query": "query myQuery { ... }", "variables": {...}}`
+//
 // and Request marshals to this format.  However, MakeRequest may
 // marshal the data in some other way desired by the backend.
 type Request struct {
@@ -112,7 +122,9 @@ type Request struct {
 // Response that contains data returned by the GraphQL API.
 //
 // Typically, GraphQL APIs will return a JSON payload of the form
+//
 //	{"data": {...}, "errors": {...}}
+//
 // It may additionally contain a key named "extensions", that
 // might hold GraphQL protocol extensions. Extensions and Errors
 // are optional, depending on the values returned by the server.

graphql/util.go

@@ -7,9 +7,13 @@ package graphql
 //
 // It is used to prevent a struct type from inheriting its embed's
 // UnmarshalJSON method, so if we construct a type:
+//
 //	type T struct { E; NoUnmarshalJSON }
-// where E has an UnmarshalJSON method, T will not inherit it, per the Go
-// selector rules: https://golang.org/ref/spec#Selectors.
+//
+// where E has an UnmarshalJSON method, T will not inherit it, per the
+// [Go selector rules].
+//
+// [Go selector rules]: https://golang.org/ref/spec#Selectors.
 type NoUnmarshalJSON struct{}
 
 // UnmarshalJSON should never be called; it exists only to prevent a sibling
@@ -22,9 +26,13 @@ func (NoUnmarshalJSON) UnmarshalJSON(b []byte) error {
 //
 // It is used to prevent a struct type from inheriting its embed's
 // MarshalJSON method, so if we construct a type:
+//
 //	type T struct { E; NoMarshalJSON }
-// where E has an MarshalJSON method, T will not inherit it, per the Go
-// selector rules: https://golang.org/ref/spec#Selectors.
+//
+// where E has an MarshalJSON method, T will not inherit it, per the
+// [Go selector rules].
+//
+// [Go selector rules]: https://golang.org/ref/spec#Selectors.
 type NoMarshalJSON struct{}
 
 // MarshalJSON should never be called; it exists only to prevent a sibling