You may strike gold soon!
That would be thanks to a new Wild Area Event in Pokemon Sword & Shield.
Starting today, you will see an increase in Magikarp raids in the Wild Area. This event will give trainers a higher chance of seeing a Shiny Magikarp.
You will also get plenty of Gold Nuggets. So you may not get yourself a gold Magikarp but you will surely still get some gold.
This Wild Area event is set to send on January 3rd.
Source: Pokemon Japan Twitter Account