Bug: Context getters have panics, silent overwrites, and inconsistent behavior #66

Summary

The rpcserver context helpers have two concrete issues:

1. Two functions panic on missing values
2. Inconsistent error-handling across getters

Bug 1: Panics

// jsonrpc_server.go:432 - PANICS if sizeKey not in context
func GetRequestSize(ctx context.Context) int {
    return ctx.Value(sizeKey{}).(int)
}

// jsonrpc_server.go:436 - PANICS if urlKey not in context  
func GetURL(ctx context.Context) *url.URL {
    return ctx.Value(urlKey{}).(*url.URL)
}

Call these outside a handler (e.g., in a test, a goroutine, or refactored code path) and they crash.

Bug 2: Inconsistent Contracts

Callers can't know which are safe without reading source.

Proposed Fix

Replace context.Value() getters with a typed wrapper (like Gin/Echo):

type RPCContext struct {
    Request     *http.Request  // guaranteed non-nil
    URL         *url.URL       // guaranteed non-nil  
    RequestSize int
    Signer      common.Address
    // ...
}

func (h *Handler) Method(rctx *RPCContext, args Args) (Result, error) {
    rctx.Request.Header.Get("X-Foo")  // always safe
}

No panics, no magic keys, explicit contracts.

Why Now

Hit this adding header logging across services. Every call site needed nil checks or risked panics. The current design makes simple tasks error-prone.