must: an alternative mechanism for fluent calls.

See the package docs string for explanation.
Signed-off-by: Eric Myhre <hash@exultant.us>

must/must.go

+// Package 'must' provides another alternative to the 'fluent' package,
+// providing many helpful functions for wrapping methods with multiple returns
+// into a single return (converting errors into panics).
+//
+// It's useful especially for testing code and other situations where panics
+// are not problematic.
+//
+// Unlike the 'fluent' package, panics are not of any particular type.
+// There is no equivalent to the `fluent.Recover` feature in the 'must' package.
+//
+// Because golang supports implied destructuring of multiple-return functions
+// into arguments for another funtion of matching arity, most of the 'must'
+// functions can used smoothly in a pointfree/chainable form, like this:
+//
+//		must.Node(SomeNodeBuilder{}.CreateString("a"))
+//
+package must
+
+import (
+	ipld "github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/impl/typed"
+)
+
+// must.Node helps write pointfree/chainable-style code
+// by taking a Node and an error and transforming any error into a panic.
+//
+// Because golang supports implied destructuring of multiple-return functions
+// into arguments for another funtion of matching arity, it can be used like this:
+//
+//		must.Node(SomeNodeBuilder{}.CreateString("a"))
+//
+func Node(n ipld.Node, e error) ipld.Node {
+	if e != nil {
+		panic(e)
+	}
+	return n
+}
+
+// must.TypedNode helps write pointfree/chainable-style code
+// by taking a Node and an error and transforming any error into a panic.
+// It will also cast the `ipld.Node` to a `typed.Node`, panicking if impossible.
+//
+// Because golang supports implied destructuring of multiple-return functions
+// into arguments for another funtion of matching arity, it can be used like this:
+//
+//		must.TypedNode(SomeNodeBuilder{}.CreateString("a"))
+//
+func TypedNode(n ipld.Node, e error) typed.Node {
+	if e != nil {
+		panic(e)
+	}
+	return n.(typed.Node)
+}