better example of how to use altsrc

[l0k18]

I had to look for quite a while to find something that was sufficiently clear that I felt confident I could use the feature. I found this, it looks quite new and even though it's half in chinese you can see how the thing works:

https://github.com/web-skeleton/skeleton

I also discovered that yaml at least v1 doesn't understand duration values. I switched to toml but I suspect yaml v2 understands durations?

What I have learned is it doesn't matter if the flag a config loads from is wrapped in an altsrc new flag (my configs contain their file location, for example) and this seems to be the best way to get a config to load from a file, but not directly from a flag string value (it uses it to construct one):

		Before: func(c *cli.Context) error {

			fmt.Println("loading configuration")
			Configure(&podConfig)
			if FileExists(*podConfig.ConfigFile) {

				inputSource, err := altsrc.NewTomlSourceFromFile(*podConfig.ConfigFile)

				if err != nil {
					fmt.Println("error -", err)
					panic(err)
				}
				return altsrc.ApplyInputSourceValues(c, inputSource, c.App.Flags)
			}
			return nil
		},

[johnwyles]

@l0k1verloren Please also look at: #800 #793 and PR's #802 #803

[coilysiren]

Hiya! There's a known issue with the current implementation of the CLI, where altsrc is generally clunky and poorly documented. My current idea is that I'm going to move all of the altsrc functionality into the main package in some way, and that's how all of the "altsrc is weird and different???" issues people are having will get resolved. I'm tracking that work here => #833