Catchment phase 1: replacing a handwritten rain log

My dad has logged rainfall by hand since 2009. Phase 1 replaces the notebook with a small Go service he can use from his phone.

What shipped

• A rain logbook: one reading a day, edits kept as history.
• Forecast snapshots from Open-Meteo, stored so I can compare forecast with measured rain later.
• A roof catchment calculator: roof area × rainfall × runoff coefficient.

The dashboard renders in 38 ms on the old OptiPlex.

Why no framework

The standard library’s net/http covered everything phase 1 needed¹.

mux := http.NewServeMux()
mux.HandleFunc("GET /readings", h.listReadings)
mux.HandleFunc("POST /readings", h.createReading)

Footnotes

1. Go 1.22 added method and wildcard patterns to ServeMux. ↩