Go: a subfolder is a separate package, so you can't move methods of a main-package type into server/rpc/

Common refactor trap in Go daemons built with net/rpc: wanting to group RPC handlers into a subfolder like server/rpc/{cli,kvs,mem}.go. Each folder is its own package, so (1) the shared type (e.g. Machine, defined in package main) is undefined there, (2) Go forbids defining methods on a type from another package, so handlers like (m *Machine) Gossip can't live there unless the type itself moves and every cross-package field/method gets exported, and (3) naming the package rpc shadows net/rpc, which those files import. Low-churn alternative: keep them in the same package as flat files with a shared prefix (rpc_cli.go, rpc_kvs.go, rpc_mem.go) so they sort together. Related tip: register a separate small type (e.g. CLI{Machine *Machine}) for client-facing commands so method names like Join don't collide with node-to-node RPCs on Machine. gob matches args by field name, not type name, so client and server can each declare their own structs as long as field names match.