Resolve value sources concurrently

I added `smol` as a minimal async runtime. It only needs to be used in a few places so I didn't bother wrapping the whole program in it. This brought the binary size from 1.4MiB up to 1.6MiB, so not bad.

Closes #61

.env-select.toml

@@ -1,10 +1,12 @@
+[applications.server.profiles.base]
+pre_export = [{setup = "echo setup", teardown = "echo teardown"}]
 
-[applications.server.profiles.base1]
-pre_export = [{setup = "echo base1 setup", teardown = "echo base1 teardown"}]
+[applications.server.profiles.dev]
+extends = ["base"]
+variables.SERVICE1 = "dev"
+variables.SERVICE2 = "also-dev"
 
-[applications.server.profiles.base2]
-pre_export = [{setup = "echo base2 setup", teardown = "echo base2 teardown"}]
-
-[applications.server.profiles.child]
-extends = ["base1", "base2"]
-pre_export = [{setup = "echo child setup", teardown = "echo child teardown"}]
+[applications.server.profiles.prd]
+extends = ["base"]
+variables.SERVICE1 = "prd"
+variables.SERVICE2 = "also-prd"

CHANGELOG.md

@@ -6,6 +6,11 @@
 
 - Pass a list of strings to `multiple` to filter which values are loaded from a mapping
 
+### Changed
+
+- Resolve values in parallel
+  - This means profile resolution will only take as long as the slowest step, rather than the sum of all steps
+
 ## [1.0.0] - 2024-02-02
 
 ### Added