@item_router.get("/")
def get_items(user_id: Optional[str] = None):
    if user_id is None:
        return [{"item_id": "i1", "user_id": "u1"}, {"item_id": "i2", "user_id": "u2"}]
    else:
        return [{"item_id": "i2", "user_id": user_id}]


@item_router.get("/{item_id}")
def get_item(item_id: str, user_id: Optional[str] = None):
    if user_id is None:
        return {"item_id": item_id}
    else:

a select with only <code>nil</code> channels and no default case blocks forever.
</p>

<pre>
var a []int
var c, c1, c2, c3, c4 chan int
var i1, i2 int
select {
case i1 = &lt;-c1:
	print("received ", i1, " from c1\n")
case c2 &lt;- i2:
	print("sent ", i2, " to c2\n")
case i3, ok := (&lt;-c3):  // same as: i3, ok := &lt;-c3
	if ok {
		print("received ", i3, " from c3\n")
	} else {

by Ard Biesheuvel <******@****.***> #include "textflag.h" #define SHA512TRANS(i0, i1, i2, i3, i4, rc0, in0) \ VADD in0.D2, rc0.D2, V5.D2 \ VEXT $8, i3.B16, i2.B16, V6.B16 \ VEXT $8, V5.B16, V5.B16, V5.B16 \ VEXT $8, i2.B16, i1.B16, V7.B16 \ VADD V5.D2, i3.D2, i3.D2 \ #define SHA512ROUND(i0, i1, i2, i3, i4, rc0, rc1, in0, in1, in2, in3, in4) \ VLD1.P 16(R4), [rc1.D2] \ SHA512TRANS(i0, i1, i2, i3, i4, rc0, in0) \ VEXT $8, in4.B16, in3.B16, V5.B16 \ SHA512SU0 in1.D2, in0.D2 \ SHA512H V7.D2,...