fix(go): a call through a func-typed struct field reaches the functions put in it

CHANGELOG.md

@@ -161,6 +161,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - In Go, a type defined over a slice, map, function or basic type now counts as implementing the interfaces its methods satisfy, just as a struct does: prometheus's `type staticDiscoverer []*targetgroup.Group` is a `Discoverer`, gin's `type formSource map[string][]string` a `setter`, etcd's `type Int64Comparable int64` a `Comparable`, and an adapter like `type HandlerFunc func(…)` a `Handler`. Before, only structs were considered, so these types were missing from an interface's implementations in `codegraph_explore`, impact and the type hierarchy, and a call through the interface, like `Discoverer.Run` or `setter.TrySet`, stopped there instead of reaching their methods. Re-index Go projects after upgrading.
 - In Go, a type alias like `type Event = mvccpb.Event`, alone or inside a `type ( … )` group, is now indexed and links to the type it names, so impact on that type reaches the code that uses the alias. Before, aliases were missing: a use written through the alias's package, like `clientv3.Event` or prometheus's `storage.AOptions{…}`, linked to nothing, and one inside the package, like `&PrometheusVersion{}` in prometheus's `web` package, linked to whichever type of that name the project had, there a test helper's struct. A method called on a value of an alias's type now reaches the aliased type's method rather than a namesake's, and a generic alias like `type Items[T any] = List[T]` links to `List`, so `xs.Len()` on one reaches `List.Len` instead of nothing. Re-index Go projects after upgrading.
 - In Go, a struct that embeds another is no longer treated as overriding the methods it redeclares. gin's `Engine` embeds `RouterGroup` and has a `Use` of its own, but calling `Use` on a `RouterGroup` only ever runs `RouterGroup.Use`; before, `codegraph_explore`'s call path and impact went on from it into `Engine.Use` and the code only the engine runs. The same held for every struct or defined type embedded in another that redeclares one of its methods, like etcd's `Mutex` inside `lockerMutex`. A call through an interface still reaches each type that implements it, the embedding struct included. Re-index Go projects after upgrading.
+- In Go, a call through a struct field that holds a function, like prometheus's `d.refreshf(ctx)`, now reaches the functions put in that field, so `codegraph_explore` follows service discovery from `Discovery.Run` into each provider's `refresh` and names the line where each provider wires its method in, like `RefreshF: d.refresh`. The field can be set in a struct literal or by an assignment, copied from another struct's field (`refreshf: opts.RefreshF`), or given a method of an interface value, and two unrelated structs with a field of the same name, like `fn` or `handler`, stay apart. Before, such a flow stopped at the field. Re-index Go projects after upgrading.
 - In Go, a type defined from other types, like etcd's `type WatchChan <-chan WatchResponse` or gin's `type HandlerFunc func(*Context)` and `type HandlersChain []HandlerFunc`, now links to the types it is built from, so impact on `WatchResponse` or gin's `Context` reaches these types and the code that uses them. Before, such a type linked to nothing. One written through another package, like etcd's `type PutResponse pb.PutResponse`, links to that package's type, and a recursive one like `type stateFn func(*Lexer) stateFn` doesn't link to itself. Re-index Go projects after upgrading.
 - In Go, a struct now links to the types its fields are declared with, like etcd's `PutResponse` holding a `*ResponseHeader` or gin's `Context` holding a `HandlersChain`, so impact on `ResponseHeader` or `HandlersChain` reaches every struct that holds one and the code that uses those structs, and `codegraph_node` lists a struct's field types. Before, a struct linked only to the types it embeds. A field written through another package, like `*pb.ResponseHeader`, links to that package's type, one from outside your project, like `context.Context`, links to nothing, the types an embedded generic is filled in with, like the `Pod` in client-go's `listers.ResourceIndexer[*v1.Pod]`, link too, and a struct that holds itself, like a list node's `next *node`, doesn't link to itself. `codegraph_explore` still answers a question about a flow with the code that runs it, not with the structs that merely hold one of its types. Re-index Go projects after upgrading.
 - In Go, an unexported name used in another file of its package, like prometheus's `memSeries` in `tsdb/head_append.go`, now links to that package's own declaration when a package nested inside it, like `tsdb/agent`, declares the same name. Before, such a parameter, result, struct field, composite literal or call linked to nothing. A call or a function value that the surrounding function binds itself, like a test's `init := func(…)` followed by `init(t)`, or a local `volumeSpec` variable passed on, no longer links to the package's declaration of that name. A name bound in one `case` of a `switch` or `select`, or a parameter named inside a function-typed result like `func() func(run string)`, is not such a binding anywhere else, so a call there still links. Thanks @inth3shadows. (#2580) Re-index Go projects after upgrading.